Related
First of all: yes, I read all the other threads on this topic. And not only those from this site... (you see, I'm a little frustrated)
Most of them come with the advice to use android:id instead of just id in the XML file. I did.
From others, I learned, that View.findViewById works different than Activity.findViewById. I handled that, too.
In my location_layout.xml, I use:
<FrameLayout .... >
<some.package.MyCustomView ... />
<LinearLayout ... >
<TextView ...
android:id="#+id/txtLat" />
...
</LinearLayout>
</FrameLayout>
In my Activity I do:
...
setContentView( R.layout.location_layout );
and in my custom view class:
...
TextView tv = (TextView) findViewById( R.id.txtLat );
which returns null. Doing this, my Activity works fine. So maybe it's because of the Activity.findViewById and View.findViewById differences. So I stored the context passed to the customs view constructor locally and tried:
...
TextView tv = (TextView) ((Activity) context).findViewById( R.id.txtLat );
which also returned null.
Then, I changed my custom view to extend ViewGroup instead View and changed the location_layout.xml to let the TextView be a direct child of my custom view, so that the View.findViewById should work as supposed. Suprise: it didn't solve anything.
So what the heck am I doing wrong?
I'll appreciate any comments.
which returns null
Possibly because you are calling it too early. Wait until onFinishInflate(). Here is a sample project demonstrating a custom View accessing its contents.
Possibly, you are calling findViewById before calling setContentView?
If that's the case, try calling findViewById AFTER calling setContentView
Make sure you don't have multiple versions of your layout for different screen densities. I ran into this problem once when adding a new id to an existing layout but forgot to update the hdpi version. If you forget to update all versions of the layout file it will work for some screen densities but not others.
FindViewById can be null if you call the wrong super constructor in a custom view. The ID tag is part of attrs, so if you ignore attrs, you delete the ID.
This would be wrong
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context);
}
This is correct
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context,attrs);
}
Alongside the classic causes, mentioned elsewhere:
Make sure you've called setContentView() before findViewById()
Make sure that the id you want is in the view or layout you've given to setContentView()
Make sure that the id isn't accidentally duplicated in different layouts
There is one I have found for custom views in standard layouts, which goes against the documentation:
In theory you can create a custom view and add it to a layout (see here). However, I have found that in such situations, sometimes the id attribute works for all the views in the layout except the custom ones. The solution I use is:
Replace each custom view with a FrameLayout with the same layout properties as you would like the custom view to have. Give it an appropriate id, say frame_for_custom_view.
In onCreate:
setContentView(R.layout.my_layout);
FrameView fv = findViewById(R.id.frame_for_custom_layout);
MyCustomView cv = new MyCustomView(context);
fv.addView(cv);
which puts the custom view in the frame.
In my case, I had 2 activites in my project, main.xml and main2.xml. From the beginning, main2 was a copy of main, and everything worked well, until I added new TextView to main2, so the R.id.textview1 became available for the rest of app. Then I tried to fetch it by standard calling:
TextView tv = (TextView) findViewById( R.id.textview1 );
and it was always null. It turned out, that in onCreate constructor I was instantiating not main2, but the other one. I had:
setContentView(R.layout.main);
instead of
setContentView(R.layout.main2);
I noticed this after I arrived here, on the site.
#Override
protected void onStart() {
// use findViewById() here instead of in onCreate()
}
A answer for those using ExpandableListView and run into this question based on it's title.
I had this error attempting to work with TextViews in my child and group views as part of an ExpandableListView implementation.
You can use something like the following in your implementations of the getChildView() and getGroupView() methods.
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) myContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.child_layout, null);
}
I found this here.
FWIW, I don't see that anyone solved this in quite the same way as I needed to. No complaints at compile time, but I was getting a null view at runtime, and calling things in the proper order. That is,
findViewById()
after
setContentView().
The problem turned out that my view is defined in content_main.xml, but in my activity_main.xml, I lacked this one statement:
<include layout="#layout/content_main" />
When I added that to activity_main.xml, no more NullPointer.
I'm pretty new to Android/Eclipse, by mistake I added the UI stuff to activity_main.xml instead of fragment_main.xml. Took me some hours to figure that out...
I had this same problem. I was using a third-party library that allows you to override their adapter for a GridView and to specify your own layout for each GridView cell.
I finally realized what was happening. Eclipse was still using the library's layout xml file for each cell in the GridView, even though it gave no indication of this. In my custom adapter, it indicated that it was using the xml resource from my own project even though at runtime, it wasn't.
So what I did was to make sure my custom xml layouts and ids were different from those still sitting in the library, cleaned the project and then it started reading the correct custom layouts that were in my project.
In short, be careful if you're overriding a third-party library's adapter and specifying your own layout xml for the adapter to use. If your layout inside your project has the same file name as that in the library, you might encounter a really difficult-to-find bug!
In my particular case, I was trying to add a footer to a ListView. The following call in onCreate() was returning null.
TextView footerView = (TextView) placesListView.findViewById(R.id.footer);
Changing this to inflate the footer view instead of finding it by ID solved this issue.
View footerView = ((LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.footer_view, null, false);
Just wanted to throw my specific case in here. Might help someone down the line.
I was using the directive in my Android UI XML like this:
Parent view:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:tag="home_phone"
android:background="#color/colorPrimary">
...
<include
layout="#layout/retry_button"
android:visibility="gone" />
Child view (retry_button):
<com.foo.RetryButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/retry"
android:layout_gravity="center"
android:orientation="vertical"
android:layout_width="100dp"
android:layout_height="140dp">
.findViewById(R.id.retry) would always return null. But, if I moved the ID from the child view into the include tag, it started working.
Fixed parent:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:tag="home_phone"
android:background="#color/colorPrimary">
...
<include
layout="#layout/retry_button"
android:id="#+id/retry"
android:visibility="gone" />
Fixed child:
<com.foo.RetryButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_gravity="center"
android:orientation="vertical"
android:layout_width="100dp"
android:layout_height="140dp">
In my case, I was using ExpandableListView and I had set android:transcriptMode="normal". This was causing few children in expandable group to disappear and I used to get NULL exception when ever I used scroll the list.
For me I had two xml layouts for the same activity - one in portrait mode and one in landscape. Of course I had changed the id of an object in the landscape xml but had forgotten to make the same change in the portrait version. Make sure if you change one you do the same to the other xml or you will not get an error until you run/debug it and it can't find the id you didn't change. Oh dumb mistakes, why must you punish me so?
Set the activity content from a layout resource.
ie.,setContentView(R.layout.basicXml);
In addition of the above solutions you make sure the
tools:context=".TakeMultipleImages"
in the layout is same value in the mainfest.xml file :
android:name=".TakeMultipleImages" for the same activity element.
it is occur when use copy and paste to create new activity
I have the same problem, but I think its worth sharing with you guys.
If you have to findViewById in custom layout, for example:
public class MiniPlayerControllBar extends LinearLayout {
//code
}
you cannot get the view in constructor.
You should call findViewById after view has inflated.
Their is a method you can override onFinishInflate
My case is none like above, no solutions worked. I assume my view was too deep into layout hierarchy. I moved it one level up and it was not null anymore.
INFLATE THE LAYOUT !! (which contains the id)
In my case findViewById() returned null, because the layout in which the element was written, was not inflated...
Eg.
fragment_layout.xml
<ListView
android:id="#+id/listview">
findViewById(R.id.listview) returned null, because I had not done
inflater.inflate(R.layout.fragment_layout, ..., ...);
before it.
Hope this answer helps some of y'all.
In my case I had inflated the layout but the child views were returning null. Originally I had this:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
pbSpinner = (ProgressBar) findViewById(R.id.pbListviewFooter);
tvText = (TextView) findViewById(R.id.tvListviewFooter);
...
}
However, when I changed it to the following it worked:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
pbSpinner = (ProgressBar) footerView.findViewById(R.id.pbListviewFooter);
tvText = (TextView) footerView.findViewById(R.id.tvListviewFooter);
...
}
The key was to specifically reference the already inflated layout in order to get the child views. That is, to add footerView:
footerView.findViewById...
It crashed for me because one of fields in my activity id was matching with id in an other activity. I fixed it by giving a unique id.
In my loginActivity.xml password field id was "password". In my registration activity I just fixed it by giving id r_password, then it returned not null object:
password = (EditText)findViewById(R.id.r_password);
In my experience, it seems that this can also happen when your code is called after OnDestroyView (when the fragment is on the back stack.) If you are updating the UI on input from a BroadCastReceiver, you ought to check if this is the case.
findViewById also can return null if you're inside a Fragment. As described here: findViewById in Fragment
You should call getView() to return the top level View inside a Fragment. Then you can find the layout items (buttons, textviews, etc)
In my case, findViewById returned null when I moved the call from a parent object into an adapter object instantiated by the parent. After trying tricks listed here without success, I moved the findViewById back into the parent object and passed the result as a parameter during instantiation of the adapter object.
For example, I did this in parent object:
Spinner hdSpinner = (Spinner)view.findViewById(R.id.accountsSpinner);
Then I passed the hdSpinner as a parameter during creation of the adapter object:
mTransactionAdapter = new TransactionAdapter(getActivity(),
R.layout.transactions_list_item, null, from, to, 0, hdSpinner);
I was facing a similar problem when I was trying to do a custom view for a ListView.
I solved it simply by doing this:
public View getView(int i, View view, ViewGroup viewGroup) {
// Gets the inflater
LayoutInflater inflater = LayoutInflater.from(this.contexto);
// Inflates the layout
ConstraintLayout cl2 = (ConstraintLayout)
inflater.inflate(R.layout.custom_list_view, viewGroup, false);
//Insted of calling just findViewById, I call de cl2.findViewById method. cl2 is the layout I have just inflated.
TextView tv1 = (TextView)cl2.findViewById(cl2);
Ways to debug and find the issue:
Comment out all findViewById in your activity.
Comment out everything except onCreate and setContentView
Run the project and see if any layout is set
In my case, I was using activity_main.xml in both my app module and also my library module. So when I performed the above steps, instead of the layout which I designed in the library, the layout inside app module was inflated.
So I changed the activity_main.xml file name to activity_main_lib.xml.
So make sure you do not have any duplicate layout names in your whole project.
The issue for me was that I had two layouts with the same file name activity_main.xml. (The layouts were in different libraries but in the same app) The issue was solved by renaming one of them to a unique name.
For me it returned null because the given control was (programmatically) hidden. When I put a condition to call findViewByID(id) only when the control is visible, it started working again.
For me it was only null when using Evaluate Expression or the Debug Watch View of the IDE.
First of all: yes, I read all the other threads on this topic. And not only those from this site... (you see, I'm a little frustrated)
Most of them come with the advice to use android:id instead of just id in the XML file. I did.
From others, I learned, that View.findViewById works different than Activity.findViewById. I handled that, too.
In my location_layout.xml, I use:
<FrameLayout .... >
<some.package.MyCustomView ... />
<LinearLayout ... >
<TextView ...
android:id="#+id/txtLat" />
...
</LinearLayout>
</FrameLayout>
In my Activity I do:
...
setContentView( R.layout.location_layout );
and in my custom view class:
...
TextView tv = (TextView) findViewById( R.id.txtLat );
which returns null. Doing this, my Activity works fine. So maybe it's because of the Activity.findViewById and View.findViewById differences. So I stored the context passed to the customs view constructor locally and tried:
...
TextView tv = (TextView) ((Activity) context).findViewById( R.id.txtLat );
which also returned null.
Then, I changed my custom view to extend ViewGroup instead View and changed the location_layout.xml to let the TextView be a direct child of my custom view, so that the View.findViewById should work as supposed. Suprise: it didn't solve anything.
So what the heck am I doing wrong?
I'll appreciate any comments.
which returns null
Possibly because you are calling it too early. Wait until onFinishInflate(). Here is a sample project demonstrating a custom View accessing its contents.
Possibly, you are calling findViewById before calling setContentView?
If that's the case, try calling findViewById AFTER calling setContentView
Make sure you don't have multiple versions of your layout for different screen densities. I ran into this problem once when adding a new id to an existing layout but forgot to update the hdpi version. If you forget to update all versions of the layout file it will work for some screen densities but not others.
FindViewById can be null if you call the wrong super constructor in a custom view. The ID tag is part of attrs, so if you ignore attrs, you delete the ID.
This would be wrong
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context);
}
This is correct
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context,attrs);
}
Alongside the classic causes, mentioned elsewhere:
Make sure you've called setContentView() before findViewById()
Make sure that the id you want is in the view or layout you've given to setContentView()
Make sure that the id isn't accidentally duplicated in different layouts
There is one I have found for custom views in standard layouts, which goes against the documentation:
In theory you can create a custom view and add it to a layout (see here). However, I have found that in such situations, sometimes the id attribute works for all the views in the layout except the custom ones. The solution I use is:
Replace each custom view with a FrameLayout with the same layout properties as you would like the custom view to have. Give it an appropriate id, say frame_for_custom_view.
In onCreate:
setContentView(R.layout.my_layout);
FrameView fv = findViewById(R.id.frame_for_custom_layout);
MyCustomView cv = new MyCustomView(context);
fv.addView(cv);
which puts the custom view in the frame.
In my case, I had 2 activites in my project, main.xml and main2.xml. From the beginning, main2 was a copy of main, and everything worked well, until I added new TextView to main2, so the R.id.textview1 became available for the rest of app. Then I tried to fetch it by standard calling:
TextView tv = (TextView) findViewById( R.id.textview1 );
and it was always null. It turned out, that in onCreate constructor I was instantiating not main2, but the other one. I had:
setContentView(R.layout.main);
instead of
setContentView(R.layout.main2);
I noticed this after I arrived here, on the site.
#Override
protected void onStart() {
// use findViewById() here instead of in onCreate()
}
A answer for those using ExpandableListView and run into this question based on it's title.
I had this error attempting to work with TextViews in my child and group views as part of an ExpandableListView implementation.
You can use something like the following in your implementations of the getChildView() and getGroupView() methods.
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) myContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.child_layout, null);
}
I found this here.
FWIW, I don't see that anyone solved this in quite the same way as I needed to. No complaints at compile time, but I was getting a null view at runtime, and calling things in the proper order. That is,
findViewById()
after
setContentView().
The problem turned out that my view is defined in content_main.xml, but in my activity_main.xml, I lacked this one statement:
<include layout="#layout/content_main" />
When I added that to activity_main.xml, no more NullPointer.
I'm pretty new to Android/Eclipse, by mistake I added the UI stuff to activity_main.xml instead of fragment_main.xml. Took me some hours to figure that out...
I had this same problem. I was using a third-party library that allows you to override their adapter for a GridView and to specify your own layout for each GridView cell.
I finally realized what was happening. Eclipse was still using the library's layout xml file for each cell in the GridView, even though it gave no indication of this. In my custom adapter, it indicated that it was using the xml resource from my own project even though at runtime, it wasn't.
So what I did was to make sure my custom xml layouts and ids were different from those still sitting in the library, cleaned the project and then it started reading the correct custom layouts that were in my project.
In short, be careful if you're overriding a third-party library's adapter and specifying your own layout xml for the adapter to use. If your layout inside your project has the same file name as that in the library, you might encounter a really difficult-to-find bug!
In my particular case, I was trying to add a footer to a ListView. The following call in onCreate() was returning null.
TextView footerView = (TextView) placesListView.findViewById(R.id.footer);
Changing this to inflate the footer view instead of finding it by ID solved this issue.
View footerView = ((LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.footer_view, null, false);
Just wanted to throw my specific case in here. Might help someone down the line.
I was using the directive in my Android UI XML like this:
Parent view:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:tag="home_phone"
android:background="#color/colorPrimary">
...
<include
layout="#layout/retry_button"
android:visibility="gone" />
Child view (retry_button):
<com.foo.RetryButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/retry"
android:layout_gravity="center"
android:orientation="vertical"
android:layout_width="100dp"
android:layout_height="140dp">
.findViewById(R.id.retry) would always return null. But, if I moved the ID from the child view into the include tag, it started working.
Fixed parent:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:tag="home_phone"
android:background="#color/colorPrimary">
...
<include
layout="#layout/retry_button"
android:id="#+id/retry"
android:visibility="gone" />
Fixed child:
<com.foo.RetryButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_gravity="center"
android:orientation="vertical"
android:layout_width="100dp"
android:layout_height="140dp">
In my case, I was using ExpandableListView and I had set android:transcriptMode="normal". This was causing few children in expandable group to disappear and I used to get NULL exception when ever I used scroll the list.
For me I had two xml layouts for the same activity - one in portrait mode and one in landscape. Of course I had changed the id of an object in the landscape xml but had forgotten to make the same change in the portrait version. Make sure if you change one you do the same to the other xml or you will not get an error until you run/debug it and it can't find the id you didn't change. Oh dumb mistakes, why must you punish me so?
Set the activity content from a layout resource.
ie.,setContentView(R.layout.basicXml);
In addition of the above solutions you make sure the
tools:context=".TakeMultipleImages"
in the layout is same value in the mainfest.xml file :
android:name=".TakeMultipleImages" for the same activity element.
it is occur when use copy and paste to create new activity
I have the same problem, but I think its worth sharing with you guys.
If you have to findViewById in custom layout, for example:
public class MiniPlayerControllBar extends LinearLayout {
//code
}
you cannot get the view in constructor.
You should call findViewById after view has inflated.
Their is a method you can override onFinishInflate
My case is none like above, no solutions worked. I assume my view was too deep into layout hierarchy. I moved it one level up and it was not null anymore.
INFLATE THE LAYOUT !! (which contains the id)
In my case findViewById() returned null, because the layout in which the element was written, was not inflated...
Eg.
fragment_layout.xml
<ListView
android:id="#+id/listview">
findViewById(R.id.listview) returned null, because I had not done
inflater.inflate(R.layout.fragment_layout, ..., ...);
before it.
Hope this answer helps some of y'all.
In my case I had inflated the layout but the child views were returning null. Originally I had this:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
pbSpinner = (ProgressBar) findViewById(R.id.pbListviewFooter);
tvText = (TextView) findViewById(R.id.tvListviewFooter);
...
}
However, when I changed it to the following it worked:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
pbSpinner = (ProgressBar) footerView.findViewById(R.id.pbListviewFooter);
tvText = (TextView) footerView.findViewById(R.id.tvListviewFooter);
...
}
The key was to specifically reference the already inflated layout in order to get the child views. That is, to add footerView:
footerView.findViewById...
It crashed for me because one of fields in my activity id was matching with id in an other activity. I fixed it by giving a unique id.
In my loginActivity.xml password field id was "password". In my registration activity I just fixed it by giving id r_password, then it returned not null object:
password = (EditText)findViewById(R.id.r_password);
In my experience, it seems that this can also happen when your code is called after OnDestroyView (when the fragment is on the back stack.) If you are updating the UI on input from a BroadCastReceiver, you ought to check if this is the case.
findViewById also can return null if you're inside a Fragment. As described here: findViewById in Fragment
You should call getView() to return the top level View inside a Fragment. Then you can find the layout items (buttons, textviews, etc)
In my case, findViewById returned null when I moved the call from a parent object into an adapter object instantiated by the parent. After trying tricks listed here without success, I moved the findViewById back into the parent object and passed the result as a parameter during instantiation of the adapter object.
For example, I did this in parent object:
Spinner hdSpinner = (Spinner)view.findViewById(R.id.accountsSpinner);
Then I passed the hdSpinner as a parameter during creation of the adapter object:
mTransactionAdapter = new TransactionAdapter(getActivity(),
R.layout.transactions_list_item, null, from, to, 0, hdSpinner);
I was facing a similar problem when I was trying to do a custom view for a ListView.
I solved it simply by doing this:
public View getView(int i, View view, ViewGroup viewGroup) {
// Gets the inflater
LayoutInflater inflater = LayoutInflater.from(this.contexto);
// Inflates the layout
ConstraintLayout cl2 = (ConstraintLayout)
inflater.inflate(R.layout.custom_list_view, viewGroup, false);
//Insted of calling just findViewById, I call de cl2.findViewById method. cl2 is the layout I have just inflated.
TextView tv1 = (TextView)cl2.findViewById(cl2);
Ways to debug and find the issue:
Comment out all findViewById in your activity.
Comment out everything except onCreate and setContentView
Run the project and see if any layout is set
In my case, I was using activity_main.xml in both my app module and also my library module. So when I performed the above steps, instead of the layout which I designed in the library, the layout inside app module was inflated.
So I changed the activity_main.xml file name to activity_main_lib.xml.
So make sure you do not have any duplicate layout names in your whole project.
The issue for me was that I had two layouts with the same file name activity_main.xml. (The layouts were in different libraries but in the same app) The issue was solved by renaming one of them to a unique name.
For me it returned null because the given control was (programmatically) hidden. When I put a condition to call findViewByID(id) only when the control is visible, it started working again.
For me it was only null when using Evaluate Expression or the Debug Watch View of the IDE.
Greetings fellow programmers!
I am building a mobile app where I fetch JSON data from an API then transfer it using bundle to next activity (all of that works perfectly). In the second activity the JSON data transferred (in the form of a string) is supposed to be used to dynamically populate fields.
Now what I am trying to do is that I am trying to extract names of the companies from my JSON data, populate them into buttons dynamically and use the rest of JSON data (such as phone numbers, emails etc) to display information only when the button (with the name of the company on it) is clicked on.
Ideally I would want to use an accordion button but after doing some research apparently it cannot be easily implemented in Android. So I was thinking of using a dialog box (with the rest of the info) that would pop up after pressing a button with the company name on it.
I am not sure where to begin to be honest with dynamical population of buttons and then dialog boxes from JSON data, so I would hoping that maybe someone from this amazing community could give me some pointers?
I would be extremely grateful for any help!!
Thank you
First you would need to parse JSON - convert it to java object.
You could either use GSON library, or do it yourself using JSONObject class.
Its quite simple, and if you are using Retrofit library for networking, there's a good chance that it does it for you.
Once you got your java models - objects created based on your JSON, just assign the values to controls. By the way, if you are using list of buttons, it is a good idea to use RecyclerView to create list.
You can find details here:
GSON library
Retrofit
Create an class for Company with members like name,address,phone-number,email etc .....
Create list of objects of Company class from json data ..
Eg :
List<Company> companies = new ArrayList<>();
jsonArray = new JsonArray(jsonInstring);
for(int i=0;i<jsonArray.length();i++){
jsonObject = jsonArray.getJsonObject(i);
company = new Company(jsonObject.getString("name"),......);
companies.add(company);
}
Now populate those data to list view or recyclerview and on click of item pass that object company and create a dialog... and inside that dialogView set value from that object to views.
Create Comapny Bean with id, name, number and other fields
Parse your json and create list of Company Bean as List<Company> companyList
In activity_main.xml file create a containerLayout for adding dynamic views
<LinearLayout
android:id="#+id/containerLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"/>
Create button_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<Button xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/button"
android:layout_width="match_parent"
android:layout_height="wrap_content"
/>
5.In your activity call addButton method
private void addButton(){
containerLayout = (LinearLayout)findViewById(R.id.containerLayout);
for(int i=0; i<companyList.size(); i++){
containerLayout.addView(generateButton(companyList.get(i)));
}
}
private Button generateButton(Company company) {
Button companyButton = (Button)getLayoutInflater().inflate(R.layout.button_layout, null);
companyButton.setText(company.getName());
companyButton.setTag(company);
companyButton.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
showPopup((Company)v.getTag()); //other details popup
}
});
return companyButton;
}
If you want to convert JSON response to your Java class object, then In that case JAKSON API will be perfect for your task.
you can convert JSON to any java object in this way.
ObjectMapper mapper = new ObjectMapper();
//Object to JSON in file
User user = mapper.readValue(new File("c:\\user.json"), User.class);
Please follow referral URL for more information.
Hope this will help you.
First of all: yes, I read all the other threads on this topic. And not only those from this site... (you see, I'm a little frustrated)
Most of them come with the advice to use android:id instead of just id in the XML file. I did.
From others, I learned, that View.findViewById works different than Activity.findViewById. I handled that, too.
In my location_layout.xml, I use:
<FrameLayout .... >
<some.package.MyCustomView ... />
<LinearLayout ... >
<TextView ...
android:id="#+id/txtLat" />
...
</LinearLayout>
</FrameLayout>
In my Activity I do:
...
setContentView( R.layout.location_layout );
and in my custom view class:
...
TextView tv = (TextView) findViewById( R.id.txtLat );
which returns null. Doing this, my Activity works fine. So maybe it's because of the Activity.findViewById and View.findViewById differences. So I stored the context passed to the customs view constructor locally and tried:
...
TextView tv = (TextView) ((Activity) context).findViewById( R.id.txtLat );
which also returned null.
Then, I changed my custom view to extend ViewGroup instead View and changed the location_layout.xml to let the TextView be a direct child of my custom view, so that the View.findViewById should work as supposed. Suprise: it didn't solve anything.
So what the heck am I doing wrong?
I'll appreciate any comments.
which returns null
Possibly because you are calling it too early. Wait until onFinishInflate(). Here is a sample project demonstrating a custom View accessing its contents.
Possibly, you are calling findViewById before calling setContentView?
If that's the case, try calling findViewById AFTER calling setContentView
Make sure you don't have multiple versions of your layout for different screen densities. I ran into this problem once when adding a new id to an existing layout but forgot to update the hdpi version. If you forget to update all versions of the layout file it will work for some screen densities but not others.
FindViewById can be null if you call the wrong super constructor in a custom view. The ID tag is part of attrs, so if you ignore attrs, you delete the ID.
This would be wrong
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context);
}
This is correct
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context,attrs);
}
Alongside the classic causes, mentioned elsewhere:
Make sure you've called setContentView() before findViewById()
Make sure that the id you want is in the view or layout you've given to setContentView()
Make sure that the id isn't accidentally duplicated in different layouts
There is one I have found for custom views in standard layouts, which goes against the documentation:
In theory you can create a custom view and add it to a layout (see here). However, I have found that in such situations, sometimes the id attribute works for all the views in the layout except the custom ones. The solution I use is:
Replace each custom view with a FrameLayout with the same layout properties as you would like the custom view to have. Give it an appropriate id, say frame_for_custom_view.
In onCreate:
setContentView(R.layout.my_layout);
FrameView fv = findViewById(R.id.frame_for_custom_layout);
MyCustomView cv = new MyCustomView(context);
fv.addView(cv);
which puts the custom view in the frame.
In my case, I had 2 activites in my project, main.xml and main2.xml. From the beginning, main2 was a copy of main, and everything worked well, until I added new TextView to main2, so the R.id.textview1 became available for the rest of app. Then I tried to fetch it by standard calling:
TextView tv = (TextView) findViewById( R.id.textview1 );
and it was always null. It turned out, that in onCreate constructor I was instantiating not main2, but the other one. I had:
setContentView(R.layout.main);
instead of
setContentView(R.layout.main2);
I noticed this after I arrived here, on the site.
#Override
protected void onStart() {
// use findViewById() here instead of in onCreate()
}
A answer for those using ExpandableListView and run into this question based on it's title.
I had this error attempting to work with TextViews in my child and group views as part of an ExpandableListView implementation.
You can use something like the following in your implementations of the getChildView() and getGroupView() methods.
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) myContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.child_layout, null);
}
I found this here.
FWIW, I don't see that anyone solved this in quite the same way as I needed to. No complaints at compile time, but I was getting a null view at runtime, and calling things in the proper order. That is,
findViewById()
after
setContentView().
The problem turned out that my view is defined in content_main.xml, but in my activity_main.xml, I lacked this one statement:
<include layout="#layout/content_main" />
When I added that to activity_main.xml, no more NullPointer.
I'm pretty new to Android/Eclipse, by mistake I added the UI stuff to activity_main.xml instead of fragment_main.xml. Took me some hours to figure that out...
I had this same problem. I was using a third-party library that allows you to override their adapter for a GridView and to specify your own layout for each GridView cell.
I finally realized what was happening. Eclipse was still using the library's layout xml file for each cell in the GridView, even though it gave no indication of this. In my custom adapter, it indicated that it was using the xml resource from my own project even though at runtime, it wasn't.
So what I did was to make sure my custom xml layouts and ids were different from those still sitting in the library, cleaned the project and then it started reading the correct custom layouts that were in my project.
In short, be careful if you're overriding a third-party library's adapter and specifying your own layout xml for the adapter to use. If your layout inside your project has the same file name as that in the library, you might encounter a really difficult-to-find bug!
In my particular case, I was trying to add a footer to a ListView. The following call in onCreate() was returning null.
TextView footerView = (TextView) placesListView.findViewById(R.id.footer);
Changing this to inflate the footer view instead of finding it by ID solved this issue.
View footerView = ((LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.footer_view, null, false);
Just wanted to throw my specific case in here. Might help someone down the line.
I was using the directive in my Android UI XML like this:
Parent view:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:tag="home_phone"
android:background="#color/colorPrimary">
...
<include
layout="#layout/retry_button"
android:visibility="gone" />
Child view (retry_button):
<com.foo.RetryButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/retry"
android:layout_gravity="center"
android:orientation="vertical"
android:layout_width="100dp"
android:layout_height="140dp">
.findViewById(R.id.retry) would always return null. But, if I moved the ID from the child view into the include tag, it started working.
Fixed parent:
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:tag="home_phone"
android:background="#color/colorPrimary">
...
<include
layout="#layout/retry_button"
android:id="#+id/retry"
android:visibility="gone" />
Fixed child:
<com.foo.RetryButton
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_gravity="center"
android:orientation="vertical"
android:layout_width="100dp"
android:layout_height="140dp">
In my case, I was using ExpandableListView and I had set android:transcriptMode="normal". This was causing few children in expandable group to disappear and I used to get NULL exception when ever I used scroll the list.
For me I had two xml layouts for the same activity - one in portrait mode and one in landscape. Of course I had changed the id of an object in the landscape xml but had forgotten to make the same change in the portrait version. Make sure if you change one you do the same to the other xml or you will not get an error until you run/debug it and it can't find the id you didn't change. Oh dumb mistakes, why must you punish me so?
Set the activity content from a layout resource.
ie.,setContentView(R.layout.basicXml);
In addition of the above solutions you make sure the
tools:context=".TakeMultipleImages"
in the layout is same value in the mainfest.xml file :
android:name=".TakeMultipleImages" for the same activity element.
it is occur when use copy and paste to create new activity
I have the same problem, but I think its worth sharing with you guys.
If you have to findViewById in custom layout, for example:
public class MiniPlayerControllBar extends LinearLayout {
//code
}
you cannot get the view in constructor.
You should call findViewById after view has inflated.
Their is a method you can override onFinishInflate
My case is none like above, no solutions worked. I assume my view was too deep into layout hierarchy. I moved it one level up and it was not null anymore.
INFLATE THE LAYOUT !! (which contains the id)
In my case findViewById() returned null, because the layout in which the element was written, was not inflated...
Eg.
fragment_layout.xml
<ListView
android:id="#+id/listview">
findViewById(R.id.listview) returned null, because I had not done
inflater.inflate(R.layout.fragment_layout, ..., ...);
before it.
Hope this answer helps some of y'all.
In my case I had inflated the layout but the child views were returning null. Originally I had this:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
pbSpinner = (ProgressBar) findViewById(R.id.pbListviewFooter);
tvText = (TextView) findViewById(R.id.tvListviewFooter);
...
}
However, when I changed it to the following it worked:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.listview_footer, null, false);
pbSpinner = (ProgressBar) footerView.findViewById(R.id.pbListviewFooter);
tvText = (TextView) footerView.findViewById(R.id.tvListviewFooter);
...
}
The key was to specifically reference the already inflated layout in order to get the child views. That is, to add footerView:
footerView.findViewById...
It crashed for me because one of fields in my activity id was matching with id in an other activity. I fixed it by giving a unique id.
In my loginActivity.xml password field id was "password". In my registration activity I just fixed it by giving id r_password, then it returned not null object:
password = (EditText)findViewById(R.id.r_password);
In my experience, it seems that this can also happen when your code is called after OnDestroyView (when the fragment is on the back stack.) If you are updating the UI on input from a BroadCastReceiver, you ought to check if this is the case.
findViewById also can return null if you're inside a Fragment. As described here: findViewById in Fragment
You should call getView() to return the top level View inside a Fragment. Then you can find the layout items (buttons, textviews, etc)
In my case, findViewById returned null when I moved the call from a parent object into an adapter object instantiated by the parent. After trying tricks listed here without success, I moved the findViewById back into the parent object and passed the result as a parameter during instantiation of the adapter object.
For example, I did this in parent object:
Spinner hdSpinner = (Spinner)view.findViewById(R.id.accountsSpinner);
Then I passed the hdSpinner as a parameter during creation of the adapter object:
mTransactionAdapter = new TransactionAdapter(getActivity(),
R.layout.transactions_list_item, null, from, to, 0, hdSpinner);
I was facing a similar problem when I was trying to do a custom view for a ListView.
I solved it simply by doing this:
public View getView(int i, View view, ViewGroup viewGroup) {
// Gets the inflater
LayoutInflater inflater = LayoutInflater.from(this.contexto);
// Inflates the layout
ConstraintLayout cl2 = (ConstraintLayout)
inflater.inflate(R.layout.custom_list_view, viewGroup, false);
//Insted of calling just findViewById, I call de cl2.findViewById method. cl2 is the layout I have just inflated.
TextView tv1 = (TextView)cl2.findViewById(cl2);
Ways to debug and find the issue:
Comment out all findViewById in your activity.
Comment out everything except onCreate and setContentView
Run the project and see if any layout is set
In my case, I was using activity_main.xml in both my app module and also my library module. So when I performed the above steps, instead of the layout which I designed in the library, the layout inside app module was inflated.
So I changed the activity_main.xml file name to activity_main_lib.xml.
So make sure you do not have any duplicate layout names in your whole project.
The issue for me was that I had two layouts with the same file name activity_main.xml. (The layouts were in different libraries but in the same app) The issue was solved by renaming one of them to a unique name.
For me it returned null because the given control was (programmatically) hidden. When I put a condition to call findViewByID(id) only when the control is visible, it started working again.
For me it was only null when using Evaluate Expression or the Debug Watch View of the IDE.
Background: I have previously asked this question on the similar topic on how to pass an instance variable from a Java class to it corresponding layout file in Android development. It turns out there is no easy way to do this, so the following is a follow-up question finding a good way to let the xml file and the class talk to each other.
Question: I am developing an game (nearly complete in Java Swing, now turning it into an Android app). It contains multiple levels, each with a differenly sized chess board and chess pieces - for all intents and purposes, it is a chess puzzle app that displays a new puzzle on a differently sized board after the player has solved the previous puzzle. The business logic is complete but I'm working on the graphics. At the game start, a static class BoardFragment (contained by BoardContainer.class) with its corresponding layout xml file fragment_board.xml should display the board size (as GridLayout) and chess pieces corresponding to the first level, which then updates as the level is completed. For clarification, the code looks somewhat like this (skip to the end to see my actual problem):
//Here is BoardFragment.class, static class contained by BoardContainer:
public static class BoardFragment extends Fragment {
public BoardFragment() {
}
public int level=0;
public void buttonPressed(View view) {
//method that will advance the game and update "level"
//depending on which button was clicked
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_board,
container, false);
return rootView;
}
}
//This is fragment_board.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.exampletest.MainGame$BoardFragment" >
<android.support.v7.widget.GridLayout
xmlns:app="schemas.android.com/apk/res-auto"
android:id="#+id/gridView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:columnCount="4" >
<ImageButton
android:id="#+id/imageButton1"
android:layout_width="49dp"
android:layout_height="49dp"
android:contentDescription="#null"
android:onClick="buttonPressed"
android:src="#drawable/grid11" />
</android.support.v7.widget.GridLayout>
</RelativeLayout>
Note that for simplicity and space, only one image button is currently in the xml file, but with app:columnCount equaling 4, there would be 16. In fact, the number should depend on the "level" instance variable in the corresponding class (so that if level==5 then perhaps app:columnCount==6 and so forth) but I'm not sure how I would commmunicate that from the class file to the xml. Is it possible at all? In fact, when the level is completed, both the board size and number of pieces should change. Should this be done by
Having one xml fragment file for each level? Then the previous question is solved, but for many levels, it would lead to many fragment files - is that best practice?
Having one fragment xml file that updates as the level is completed?
I appreciate any help.
As mentioned in the other answers, you will need to create the layout for your board dynamically at runtime. However, you can still define your individual Views and their attributes in XML layout resources, thus retaining the advantages they provide of separating the non-essential parts of the layout from the code and allowing automatic resolution of configuration-specific layouts.
For example, your layout could be adapted to separate layout resources for the board and cell layouts:
fragment_board_grid.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.exampletest.MainGame$BoardFragment" >
<android.support.v7.widget.GridLayout
android:id="#+id/gridView"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
fragment_board_cell.xml
<ImageButton xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="49dp"
android:layout_height="49dp"
android:contentDescription="#null"
android:onClick="buttonPressed"
android:src="#drawable/grid11"
tools:context="com.example.exampletest.MainGame$BoardFragment" />
These can now be dynamically inflated to create a board:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_board_grid,
container, false);
GridLayout boardLayout = (GridLayout) rootView.findViewById(
R.id.gridView);
boardLayout.setColumnCount(columnsNum);
boardLayout.setRowCount(rowsNum);
for (int columnIndex = 0; columnIndex < columnsNum; columnIndex++) {
for (int rowIndex = 0; rowIndex < rowsNum; rowIndex++) {
ImageView cellView = (ImageView) inflater.inflate(
R.layout.fragment_board_cell, boardLayout, false);
// Here you can customize it, add listeners, etc.
boardLayout.addView(cellView);
}
}
return rootView;
}
Upon starting the next level you will need to reinflate the board layout from scratch. You can approach this in two ways:
Make each instance of your Fragment represent a particular board. This would make the Fragment logic extremely simple and focused on only one game level. The logic for starting a new level would be handled by it's Activity, by replacing the existing Fragment with a new instance. This would also have the advantage of making animations for starting a new level extremely easy to implement, as FragmentTransactions have inherent support for animations.
Have the Fragment handle everything. This could be achieved by creating a generic method that would inflate a new board layout on demand and delegate to it from the onCreateView() callback, then implementing a method that would remove the current Fragment layout from it's parent and replace it with a fresh layout generated by the board-inflating method. The layout root can be gotten from the getView() method (or in case of the support library it's first child, as the library wraps the initial Fragment layout in order to block the View state from being saved by the Activity).
A good way to handle your layouts dynamically is to generate them programmatically. It's not as easy as laying everything out in an XML file, but it will provide you with much more flexibility. Here is an example:
How to create a RelativeLayout programmatically with two buttons one on top of the other?
You could always build your views dynamically in code based upon the level rather than having your views be static in nature via use of the xml file
For example...
//the layout you will work with
GridLayout layout = (GridLayout) findViewById(R.id.gridLayout);
//properties for button
Button btn = new Button(this);
btn.setLayoutParams(new LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT)); //this will depend how you want the view to look
btn.setText("My button created programmatically");
btn.setId(someId);
//add button to the layout
layout.addView(btn);
if(level == whateverlevel){ //pseudo code here obviously
//make a new button/buttons in here like above and add it to your view depending on your level
}