Please Read My Question Carefully
I am learning Activity LifeCycle. I only have one EditText and a TextView in my XML layout With certain id. When I rotate the screen, nothing seems to change because Rotation doesn't affect EditText. But when I remove the id of EditText in XML and rotated the screen, The Rotation Starts affecting and the text in the editText removed due to rotation. I am confused about the relation of EditText with its Id.
I tried to explain the problem below in columns:
Explanation of below Column names
Having Id: Does EditText has id?
Rotation : Phone has Rotated or not
EditText : What happen to EditText After Rotation.
.
Having Id----------------Rotation---------------EditText
Yes Rotated Does not change
No Rotated Yes, Text Removed from editText
MainActivity.java is empty and main_activity.xml code is below:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent">
<EditText
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ems="10"
android:hint="Enter here"
android:inputType="textPersonName"
android:textSize="26sp"
android:textStyle="bold"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.371" />
<TextView
android:id="#+id/textView2"
android:layout_width="85dp"
android:layout_height="25dp"
android:layout_marginTop="88dp"
android:text="TextView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.496"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
Sorry for using bad English and High-resolution pictures as I have no other ways. Best Regards
One of the most important aspects in Android programming is to handle the configuration changes and most common of them is orientation changes. Although it is not recommended to handle configuration changes yourself, due to the hidden complexity of handling the configuration changes, there are cases where we might need to handle manually.
If you need to save the state, the common approach is to implement onSaveInstanceState to store & restore the values which are passed as Bundle.
Coming back to your question:
Relation of EditText with its Id in Android Studio?
When it comes to saving state of View Android OS automatically calls the View.onSaveInstanceState method on each of the views in your view hierarchy as long as you call through to the super method in onSaveInstanceState. In order to restore the data, it uses android:id attribute key for that particular View’s state.So for your case, when you don't provide the id for EditText, the View's state won't be stored due to missing key.
Hope this clarifies the relationship of id to EditText
When you rotate screen on android all activities and fragments in your application are destroyed and then recreated. Android does this so that your application can reload resources based on the new configuration.
When the system destroys the activity (e.g. when the screen rotates) then although the actual Activity instance is gone, the system remembers that it existed. The system creates a new instance of that activity using a set of saved data that describes the state of the activity when it was destroyed.
when your assign an id to a view it seems that android keeps track of that view. Hence it remembers it's state.
Okay when you rotate the device this is considered as a configuration change, so the system recreates the activity and data is lost.
One way to avoid this is go to the manifest and for your specific activity add this
android:configChanges="orientation|screenSize"
here:
<activity
android:name=".YourActivityName"
android:configChanges="orientation|screenSize"
....
...
This makes the system ignore the rotation of device.
In manifest of your app, add this line to activity tag:
android:configChanges="keyboardHidden|orientation|screenSize"
The reason for this is due to Android basically destroying the activity and creating it again every time you rotate the device. This is mainly to allow for different layouts based on portrait/landscape mode.
When you use id for your component, data will be assigned to its id, but when it hasn't id, it will be recreated and data will be disappeared after rotation.
See these questions and read their good answers, I don't copy and paste them:
1- TextView's text disappearing when device rotated
2- Handle screen rotation without losing data - Android
EditText is a focused view, so in PhoneWindow, it's state will be saved automatically in saveHierarchyState() method. Only EditText with id is going to save text.
Okay, the relation of one specific EditText item to its id is: "one to one" or "one to N". One EditText item in one layout.xml has one id, if you've configured it in the layout.xml. If you've defined more than one layout.xml's and the very same EditText item (having the same id) in more than one layout.xml's, then EditText has a "one to N" relation.
Related
I want EditText not to extend IME when it is focused on Android Wear.
I read and implemented in the same way as the following thread:
Prevent EditText from automatically focusing
However, IME appears.
Is it impossible to hide IME for an EditText on Android Wear?
I tried 3 methods:
Added the following code in the onCreate() method:
{getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);}
Added the following code in the activity tag in AndroidManifest.xml
android:windowSoftInputMode="stateAlwaysHidden"
Added the following code in rect_activity_main.xml
<LinearLayout
android:layout_width="0dp"
android:layout_height="0dp"
android:background="#android:color/transparent"
android:focusable="true" android:focusableInTouchMode="true"/>
None of them worked.
Best regards, gellpro
Check Show the Input Method On Demand. It's noted that the system hides the input method when the user finishes the task in the test field or the user can hide it with a system control. With this, try to specify how your UI should respond. It's mentioned that,
To declare your preferred treatment in an activity, use the android:windowSoftInputMode attribute in your manifest's element with one of the "adjust" values.
Then, to implement hiding IME, try using InputMethodManager with constant set to RESULT_UNCHANGED_HIDDEN. This will flag for the ResultReceiver result code from showSoftInput(View, int, ResultReceiver) and hideSoftInputFromWindow(IBinder, int, ResultReceiver): the state of the soft input window was unchanged and remains hidden.
Hope that helps.
I am developing an android app as an educational project. I have created a GridView object, which uses a custom GridAdapter. The grid, as default, loads a set of placeholder images. I want the user to be able to replace those placeholder images with either their own image, some text, or a link to a youtube video.
I can't find any info on whether this is feasible. I specify an Imageview in my XML file, so I don't know how I could change this at run time? I wondered if I should create a TextView object in the XML, and layer them, and then create a method that brings one to the front? Any advice at all would be very much appreciated. It would be great to know if it's doable or not.....
<ImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="#+id/imageView"
android:layout_centerInParent="true"
/>
My suggestion is define TextView etc. in xml with gone visibility. When user has some actions get visible them and set visibility gone of ImageView.
Set the visibilities of the container based on user input... What ever user chooses make tat container visible and other two as Gone... This would work
I've built a View which displays data driven by the respective Java Activity class. The data comes from the first element of a Collection.
On a button click from the view (onClick), I want to display the second element of the Collection in the view (replacing the first element).
What is the best way to achieve this? Here is what I was thinking:
onClick invokes a method in the Activity class which modifies the state of existing view elements?
onClick reloads the Activity and the state of the Collection still exists to be able to present?
Some other way?
Not sure if 1 will work as the Model isn't bound to the view elements? Some kind of refresh will be needed.
2 sounds overkill if you just want to keep the view structure the same but modify the state of elements.
Thanks in advance.
Use ViewSwitcher
<ViewSwitcher
android:id="#+id/viewswitcher"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<View
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="firstClick" />
<View
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/ic_launcher" />
android:onClick="secondClick"
</ViewSwitcher>
In java code
firstClick()
{
viewswitcher.setDisplayedChild(1);
}
secondClick()
{
//whatever you need
}
Here when you click on a the first view(It can be a button), the second view can be made visible by replacing the first one. Use it as per your convenience.
I was over thinking this. All I had to do was update the state of the view objects in the java layer and the view would automatically 'paint' the changes.
In my app, users can either take a picture or record a video. The file is then saved and its path is passed through an intent to the next activity, which displays it for editing.
My question is, how can I easily use the same view for either a video or an image?
I tried dynamically adding a view at runtime when I know what the file type is, but it turned out to be too hard to configure, not to mention the issues that VideoViews have with being rotated.
Edit:
I forgot to mention that using the same view would be preferable, since I'm not actually going to do anything to the contents that's specific to each kind of view.
Add both the ImageView and VideoView in your layout. Then set the visibility to GONE or VISIBLE for the one you want.
You can create two child views, one for the image and one for the video. And depending on the type of your view you can hide/show your child views.
You can also use FrameLayout for this
By using frame layout / Relative layout you can place a view on top of another view. After creating the views like i mention and using the visibility Gone & Visible you can manage to handle it..
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<ImageView
android:id="#+id/ImageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="#drawable/my_drawable"
android:scaleType="fitCenter"
android:visibility="gone"/>
<VideoView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|center"
android:padding="5dp"
android:id="#+id/VideoView"
android:visibility="gone"/>
</FrameLayout>
Then based on your usage you can control it dynamically like below
// register the views
ImageView mImageView= (ImageView)findViewById(R.id.ImageView);
VideoView mVideoView= (VideoView)findViewById(R.id.VideoView);
// check your conditions like show video view r image view here
if(VideoView)
{
mVideoView.setVisibility(View.VISIBLE);
mImageView.setVisibility(View.GONE);
}
else if(ImageView)
{
mImageView.setVisibility(View.VISIBLE);
mVideoView.setVisibility(View.GONE);
}
Hope it will work for you :)
I want to create a ListView and a few other text boxes for filtering the list.
Is there a way to make it happen using one activity (i.e at the same page)?
One more question:
May I modify a ListView directly without creating a ListActivity? and how do I make the ListView in my ListActivity visible? (how do I link it with the xml?).
Yes. ListActivity seems to cause a lot of confusion for people, when all it is, is a regular activity with a ListView as the content, some helper methods, and that's it.
To add your own, create a new layout file and add all the widgets you need like you would any other layout file. Example:
<LinearLayout xmlns:android="http://schemas.android.com/res/apk/android"
android:weightSum="1.0"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/whatever"
android:layout_weight="0" />
<ListView
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1" />
</LinearLayout>
You certainly can create a layout which contains both a ListView and other controls! Make your Activity have a layout which contains both your ListView and your other controls.
<RelativeLayout>
<ListView android:id="#+id/listy"/>
<Button android:id="#+id/buttony"
android:layout_below="#id/listy"/>
</RelativeLayout>
In your Activity, you'll still need to hook up your data adapter to the ListView and so forth.
Yes, you can have ListView together with some other required views with in the same Activity. The way I would do this is to define an Activity and add ListView (with width and height set to fill_parent) and add a SlidingDrawer which contains all the options required to alter ListView. With this approach, your ListView will take up all the space on screen and offering user to interact freely. However, on the other hand, SlidingDrawer will give give extra space for all the list altering views/options.