Develop Reference

Getting a button to work in the list view

I am new to android and my code has got a bit messy. I have successfully created a list view extended from item_layout.xml. When I click on the list view It works exactly how I want it. However in each item of the list view I have a button that when clicked I want the item of the list to delete.
When researching I have come across that you need to create a customer adapter to do this however I have come so far in the project that I wouldn't even know where to start.
This code it used successfully to when the list items are clicked it works. This is just put in the Main Activity class
mylist.setOnItemClickListener(
new AdapterView.OnItemClickListener(){
#Override
public void onItemClick(AdapterView<?> parent, View view, final int position, long id) {
}
}
);
I populate the list using this function just outside the main activity class. It is needed to be written like this as It gets the items from a database and has to be called depending on different circumstances
private void populatelistView() {
Cursor res = userDb.getAllRows();
String[] fromFeildnames = new String[]{ DatabaseUser.KEY_1, DatabaseUser.KEY_2};
int[] toViewIds = new int[]{R.id.textViewNum, R.id.textViewItem};
SimpleCursorAdapter myCursorAdaptor;
myCursorAdaptor = new SimpleCursorAdapter(getBaseContext(), R.layout.item_layout, res, fromFeildnames, toViewIds, 0);
//ListView mylist = (ListView) findViewById(R.id.listViewID);
mylist.setAdapter(myCursorAdaptor);
}
I would like to be able to get the button on each items to work by not changing much of what I have already written. I have tried just using the following code. But because it is in a different xml layout it display an error of null reference towards the item button
delete.setOnClickListener(
new View.OnClickListener() {
#Override
public void onClick(View v) {
View parentRow = (View) v.getParent();
ListView listView = (ListView) parentRow.getParent();
final int position = listView.getPositionForView(parentRow);
Toast.makeText(getApplicationContext(), "Button " + position, Toast.LENGTH_SHORT).show();
}
}
);
Please could someone help me make the button work without changing much code or give me a step by step tutorial on how to add an adapter but make my populateListView function do the same thing.
Ps. I have looked at so many tutorials about list adapters but can't find ones that are for my specific need

Custom adapter's asynchronous behaviour

I have created my own custom adapter class in my android app and I am calling it from one of my activity. I am adding some elements to the view from the adapter class and I need to access those variables from my activity class.
Now, ideally I would expect it to fill the view and then execute the further code in my activity class, but adapter class is taking some time to populate the view and in the meanwhile further code in my activity class is getting executed where no such elements have been added yet.
How do I handle this situation? I come from a js background. Do we have something like promises in java?
According to the answers I have my changed my code to this:
public class HomeActivity extends Activity {
GridView grid;
String text[] = {"Calendar","Uber","Weather","News","Youtube","Clock","Email","Maps","Twitter","Facebook"};
String list_app_name[] = {"calendar","uber","weather","news","youtube","clock","email","maps","twitter","facebook"};
String id_button[] = {"button_calendar","button_uber","button_weather","button_news","button_youtube","button_clock","button_email","button_maps","button_twitter","button_facebook"};
int image[] = {R.drawable.social_icons1,R.drawable.social_icons2,R.drawable.social_icons3,R.drawable.social_icons4,
R.drawable.social_icons5,R.drawable.social_icons6, R.drawable.social_icons7,R.drawable.social_icons8,
R.drawable.social_icons9,R.drawable.social_icons10};
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mDrawerToggle;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.activity_home);
//setting up the adapter for gridView
grid = (GridView)findViewById(R.id.simpleGrid);
ImageAdapter ia = new ImageAdapter(this,image,text,id_button);
grid.setAdapter(ia);
ia.notifyDataSetChanged();
try {
initStateOfApps();
} catch (JSONException e) {
e.printStackTrace();
}
}
public void initStateOfApps() throws JSONException {
Log.d("here","here");
ArrayList<String> list = getEnabledApps();
Log.d("apps",list.toString());
for(int i=0;i<list.size();i++) {
String app_name = list.get(i);
ToggleButton button=null;
if(app_name.equals("calendar")) {
button = (ToggleButton)findViewById(R.id.button_calendar);
button.setChecked(true);
}
}
}
}
So what is happening is that I am creating some toggle buttons that are getting populated in the ImageAdapter class that I wrote.
Once the ImageAdapter is called, I call the notifydatasetchanged() on the adapter in order to update the view.
What I am doing inside the adapter is giving each of the toggle buttons some custom ID I wrote in res/values/ids.xml.
After using setId on each of the toggle buttons, I try using that ID in my activity class but it gives me nullPointerException in the initStateOfApps() where I am trying to change the state of button.
So even after using the notifyDataSetChanged it is still behaving the same.
ImageAdapter.java
public class ImageAdapter extends BaseAdapter {
private Context context;
private final int item_image[];
private final String item_text[];
private final String button_id[];
public ImageAdapter(Context context, int item_image[], String[] item_text,String[] button) {
this.context = context;
this.item_image = item_image;
this.item_text = item_text;
this.button_id = button;
}
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View gridView;
if (convertView == null) {
gridView = new View(context);
// get layout from custom_gridview.xml
gridView = inflater.inflate(R.layout.item, null);
// set value into imageview
final ImageView image = (ImageView) gridView.findViewById(R.id.item_image);
image.setImageResource(item_image[position]);
// set value into textview
TextView text = (TextView) gridView.findViewById(R.id.item_text);
text.setText(item_text[position]);
final ToggleButton button_ = (ToggleButton) gridView.findViewById(R.id.item_button);
if(position==0) {
button_.setId(R.id.button_calendar);
image.setId(R.id.image_calendar);
}
button_.setOnCheckedChangeListener( new CompoundButton.OnCheckedChangeListener()
{
#Override
public void onCheckedChanged(CompoundButton toggleButton, boolean isChecked)
{
if(context.getResources().getResourceEntryName(toggleButton.getId()).equals("button_calendar")) {
if(isChecked) {
try {
setStateOfApp("calendar","true");
} catch (JSONException e) {
e.printStackTrace();
}
Intent intent = new Intent(context, GoogleApp.class);
((Activity) context).startActivityForResult(intent,10);
} else {
try {
setStateOfApp("calendar","false");
} catch (JSONException e) {
e.printStackTrace();
}
}
}
}
}
} else {
gridView = (View) convertView;
}
return gridView;
}
}

You are trying to access View which is not a part of Activity's content view. So you can't access that view directly.
button = (ToggleButton)findViewById(R.id.button_calendar); // will return null
This ToggleButton will be null because findViewById will fail to find out ToggleButton in current content view because that view is present in your Adapter not in content view.
And you are getting nullpointerException because you are trying to access property on null view.
button.setChecked(true); // This button is null

In java we have <Future>, but I don't think it's what you're looking for.
The adapter (extending BaseAdaper) behaviour lets you create the adapter and, even in a second moment, change underlying data via getAdapter().setData() or whatever method you choose to add.
From this perspective, the adapter is a "stupid" component acting as A View containers, you should retrieve data elsewhere (CursorAdapter is different).
So, in your Activity, fill the adapter with needed data and, when finished, call adapter.notifyDatasetChanged(). This will inform the adapter that its own data has changed and it must refresh views

Yes, ideally, the population of the adapter should be coming from the outside. The adapter should really just take in a list of data and map that data to the views. For example, some method or task in the Activity could produce a list of data (probably asynchronously...since you mentioned it) that you then pass into the adapter and then you can notifyDataSetChanged() if you need to.
I can't see your code, but if for some reason the data is truly required to be populated from inside the adapter, you could use an event bus and subscribe to it in the Activity. I would recommend going with the first option, but here are some links if you choose to use an event bus:
https://github.com/greenrobot/EventBus
http://square.github.io/otto/

As per my understanding with your question
You are not properly managed the adapter data in your activity.
If any of the data or code interlinked with your adapter data or values
Then you can start those code after you retrieve the values or data and update the view in your activity.
Please note that use Viewholders in adapter to avoid slow populating and scrolling in listviews.
Viewholders will smooth your process.
I personally suggest you that
Please go with Recyclerview and RecyclerViewAdapter.
So many Android developers are using it.
If you have background tasks in adapter you can prefer to use RX Java or EventBus
If you provide the code
It's better for us to suggest exact solution

Android ArrayList: Store Multiple Values Into A Profile

I have multiple variables, we'll call them varA, varB, varC, and varD. When a button is pressed these 4 variables are to be stored in an ArrayList, together. This creates a single entry which can be viewed by variable varA. All the entries can be viewed in a ListView which is done through an ArrayAdapter.
onCreate
ArrayAdapter<String> profileAdapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, arrayList);
profileList.setAdapter(profileAdapter);
When a button is pressed
// Add data to a new profile in #+id/profileList ListView
ArrayList<String> arrayList= new ArrayList<>();
arrayList.add(varA);
System.out.println("varA's");
System.out.println(arrayList);
((ArrayAdapter)profileList.getAdapter()).notifyDataSetChanged();
Layout
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/overviewLayout">
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/profileList"/>
</RelativeLayout>
I am having issues with the ListView showing the items that were added. Also, I was trying to use TinyDB to store these items so they can be referenced later since that ArrayList used on button press is just temporary. I also I'm having trouble figuring out how to set this up so that each time the button is pressed those 4 vars will stay together in a "profile" so they don't get mixed up with some other data that might be added later.

To avoid repeated values from getting stored check if it already exists :
if(!arrayList.contains(varA)){
arrayList.add(varA);
}
For listview updation problem ,use notifyItemInserted(position) instead of notifyDataSetChanged()
yourAdapter.notifyItemInserted(position);

As I understand, you want to display a list which contains 4 datas in one entry and showing just the first of them.
If it is, you could create a custom Model, it will be easier. This will store your datas in one object:
ProfileModel
|
|-- varA
|-- varB
|-- varC
'-- varD
Your custom model could look like something like this:
public class ProfileModel {
private String varA;
private float varB;
private int varC;
private String varD;
// getters
...
// setters
...
public ProfileModel() { }
}
Initialize the list of profiles at start:
ArrayList<ProfileModel> list = new ArrayList<>();
To populate the main list do as follows:
// create a list of object to the datas
ProfileModel profile = new ProfileModel();
profile.setVarA(varA);
profile.setVarB(varB);
profile.setVarC(varC);
profile.setVarD(varD);
// then fill the first list
list.add(profile);
Since you want to fill the adapter with other datas than a simple String but a custom model, I'd prefer to use a custom adapter. It's not that hard to create one, and because sometimes, you maybe want a different behavior on an update, I'd also prefer to use a custom notifyDataSetChanged method.
So, here's a simple adapter with the same layout as the one you used:
public class ProfileAdapter extends BaseAdapter {
private Context context;
private ArrayList<ProfileModel> listProfiles;
public ProfileAdapter(Context context, ArrayList<ProfileModel> listProfiles) {
super();
this.context = context;
this.listProfiles = listProfiles;
}
private class ViewHolder {
private TextView textVarA;
}
#Override
public int getCount() {
return listProfiles != null ? listProfiles.size() : 0;
}
#Override
public Object getItem(int i) {
return listProfiles.get(i); // will return the profile model from position
}
#Override
public long getItemId(int i) {
return i;
}
#Override
public View getView(int position, View view, ViewGroup viewGroup) {
ViewHolder holder;
if (view == null) {
holder = new ViewHolder();
view = LayoutInflater.from(context)
.inflate(android.R.layout.simple_list_item_1, null);
holder.textVarA = (TextView) view.findViewById(android.R.id.text1);
view.setTag(holder);
} else {
holder = (ViewHolder) view.getTag();
}
ProfileModel profile = listProfiles.get(i);
holder.textVarA.setText(profile.getVarA()); // get varA value
return view;
}
public void addEntry(ProfileModel newEntry) {
listProfiles.add(newEntry);
this.notifyDataSetChanged();
}
}
Then, you can set the adapter as follows:
ProfileAdapter profileAdapter = new ProfileAdapter(this, list);
profileList.setAdapter(profileAdapter);
To update this adapter:
// create a list of object to the datas
ProfileModel profile = new ProfileModel();
profile.setVarA(varA);
profile.setVarB(varB);
profile.setVarC(varC);
profile.setVarD(varD);
profileAdapter.addEntry(profile); // this will call notifyDataSetChanged
Finally, I'm not very aware about TinyDB, but I saw it's using some JSON file to store data. So you could create a method to convert your datas to JSONArray which its name is varA and has values varB, varC, varD. There is many examples how to convert datas to JSON (as using Gson to convert your model to a JSON format).
Hope this will be useful.

Android ListView: How to add a row with a buttonclick

I have a listview. In it, each row had a text saying 0:00. But now, I added a button on my actionbar but then I got stuck. I don't know how to make the button create a new row, displaying 0:00
This is my code for the data in a row.
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
RowData rowdata_data[] = new RowData[]
{
new RowData("0:00")
};
RowdataAdapter adapter = new RowdataAdapter(this,
R.layout.listview_item_row, rowdata_data);
listView1.setAdapter(adapter);
listView1 = (ListView)findViewById(R.id.listView1);
}
this is my RowData class:
public class RowData {
String title;
public RowData(String title) {
this.title = title;
}
}
So how should I implement a button click to add another row?
Under addtionbutton: should be the method.
public boolean onOptionsItemSelected(MenuItem item)
{
// Handle presses on the action bar items
switch (item.getItemId())
{
case R.id.additionbutton:
return true;
default:
return super.onOptionsItemSelected(item);
}
}

I don't know how to make the button create a new row
With your current solution it's not possible (in efficient way do it) because you're using static array of objects - it means array has fixed size (it means that you're assuming that size won't be changed at runtime).
But your goal is "slightly" different. You want after each click on Button increase number of objects by one. It means you don't know exactly how many rows you can have (or can be changed at runtime).
Due to things mentioned above you should (have to) use dynamic array with changeable size. For this reason you need to use as source of data List that is representation of dynamic array.
Basic algorithm:
Create new List with zero (or you can have by default one row at
start).
Then create public method in your adapter that will add new item to
collection and send request that Adapter should be refreshed (after you added new row into collection).
Assign OnClickListener to your Button and in onClick() method you'll use created method for adding new row into ListView.
Solution:
How to initialise ListAdapter:
// Activity-level variable scope
private List<RowData> items = new ArrayList<RowData>();
private RowdataAdapter adapter;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
listView1 = (ListView)findViewById(R.id.listView1);
// adding first item to List, it's optional step
items.add(new RowData("0:00"));
adapter = new RowdataAdapter(this, R.layout.listview_item_row, items);
listView1.setAdapter(adapter);
}
Method for adding new row into ListAdapter:
public void addRow(RowData newRow) {
// items represents List<RowData> in your Adapter class
this.items.add(newRow);
// sends request to update ListAdapter
notifyDataSetChanged();
}
How to update Adapter after click on Button:
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
// add new row to Adapter
adapter.addRow(new RowData("0:00"));
}
});
Hope i helped you to solve your problem.

you need to create a dataset that you can change so you need to make your array a class wide variable so you can add to it when you need to
when you add the new row you need to notify the adapter that something changed so you do this
adapter.notifyDatasetChanged();
and that should update your list

How to switch activity with item specific data sent

I've had a look around, and it might be because I'm not sure what I'm looking for, but I can't find out how to do something I presume should be quite easy with android.
I have an array of data to display on the screen. This data is a class that holds a database key, name and image.
I'm currently displaying this data as an ImageView and a TextView. I loop through the array and add a new row to a TableLayout containing the image and text.
I'd like both the image and text to be clickable, changing to a new activity.
This new activity needs to know the database key of the row clicked in order to display the correct data.
Here's what I have so far:
private void fillSuggestionTable(TableLayout tabSuggestions, Suggestion[] arrToAdd)
{
for(int i = 0; i < arrToAdd.length; i++)
{
/* Create a new row to be added. */
TableRow trSuggestion = new TableRow(this);
trSuggestion.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,LayoutParams.WRAP_CONTENT));
/* Create objects for the row-content. */
ImageView imgDisplayPicture = new ImageView(this);
ImageHandler.loadBitmap(arrToAdd[i].strImageURL, imgDisplayPicture);
imgDisplayPicture.setLayoutParams(new LayoutParams(50,50));
TextView txtArtistName = new TextView(this);
txtArtistName.setText(arrToAdd[i].strName);
txtArtistName.setTextColor(Color.parseColor("#000000"));
/* Add data to row. */
trSuggestion.addView(imgDisplayPicture);
trSuggestion.addView(txtArtistName);
/* Add row to TableLayout. */
tabSuggestions.addView(trSuggestion, new TableLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT));
}
}

Is there a reason you're using a TableView? it seems like what you want to accomplish would be much easier with a ListView & custom CursorAdapter, where the adapter can handle translating from the database to the ListView row. At that point starting a new activity that knows the database ID is trivial:
mListView.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick (AdapterView<?> parent, View view, int position, long id) {
Intent i = new Intent(MyActivity.this, MyOtherActivity.class);
i.putExtra("database_id", id);
startActivity(i);
}
});
And in MyOtherActivity:
private int dbId;
protected void onCreate(Bundle savedInstanceState) {
//do stuff
dbId = getIntent().getIntExtra("database_id", -1); // the -1 is the default if the extra can't be found
}

To pass extra data to another Activity, you need to add extra information with the Intent.putExtra(name, value) methods.
For example, to send the Intent:
Intent i = new Intent([pass info about next Activity here]);
i.putExtra("databaseKey", databaseKey);
startActivity(i);
To get the data out again:
public void onCreate(Bundle savedInstance)
{
// Do all initial setup here
Bundle extras = getIntent().getExtras();
if (extras != null && extras.containsKey("databaseKey"))
{
int databaseKey = extras.getInt("databaseKey");
// Load database info
}
else
{
// No data was passed, do something else
}
}
EDIT: To find out when the table's row is clicked, you'll need to implement View.OnClickListener and set the onClickListener for the TableRows you use.
For example:
/* Create a new row to be added. */
TableRow trSuggestion = new TableRow(this);
trSuggestion.setOnClickListener([listener]);
The only problem you'll have is relating a View's ID to the related database row ID. A HashMap should help.

This is a pretty simple procedure. This blog explains it in simple terms.