How to retain image in Android when screen rotation occurs

If you are programming an Android app and you’re allowing your users to select an image from gallery you will soon discover that as the screen rotates the image disappears!

Gosh! What’s happening?!

Let’s go a step back.

So far you should know that activities have a specific lifecycle. Each activity lives in different stages of its lifecycle during application usage.

The activity instance goes its journey through the following stages when it is created:

created (transient) –> started (transient) –> resumed.

When the users starts leaving the activity/application both temporarily or not, then the activity starts going down the other way:

paused (partially obscured) –> stopped (hidden) –> destroyed

So each time a users starts interacting with another activity of the same app or with another app, the current foreground activity goes to background and goes to the paused or stopped state.

If the user interaction with the app makes clear to Android that the activity is no more needed then the activity is destroyed.

If a phone call arrives or the application is put in the background, then the activity stays in the stopped state waiting to be resumed.

If the activity is not destroyed it keeps being in memory with all of its state retained and it will be fully resumed if needed.

See here for a full graph and explanation: Activity Lifecycle

What happens when it is destroyed?

One More Hidden Scenario – Screen Rotation

So what to do then?

The Wrong Answer

When destroying activities for its own purposes, Android preserves the activity status in a key-value pair blob dictionary (Bundle).
All the activity done by the user interacting with the Views in the layout is preserved in this activity state dictionary.

This means the text entered into an EditText for instance.
If you have other application specific state stored in private members of the Activity you need to add specific code to store it in the Bundle and to retrieve it from there when activity is recreated.

The events exposed to add our code are:

onSaveInstanceState and on RestoreInstanceState

You can add your persistence logic in the first one by adding key value pairs to the bundle.
You can then retrieve your values in the second event or in the onCreate event as well.

You can find detailed explanation and example here: Persist Activity State

This is the usual answer you will find on forums but it’s not applicable for Bitmaps.

The Right Answer

setRetainInstance(true);

The Fragment does not need to have an associated Layout.

Create the Fragment:

import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.v4.app.Fragment;

public class ImageRetainingFragment extends Fragment {
    private Bitmap selectedImage;

    @Override    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // retain this fragment        
        setRetainInstance(true);
    }

    public void setImage(Bitmap selectedImage) {
        this.selectedImage = selectedImage;
    }

    public Bitmap getImage() {
        return this.selectedImage;
    }
}

Add the Fragment to the Activity:

private static final String FRAGMENT_NAME = "imageFragment";
...

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    ....

    initializeImageRetainingFragment();
    tryLoadImage();
}


private void initializeImageRetainingFragment() {
    // find the retained fragment on activity restarts    
    FragmentManager fragmentManager = getSupportFragmentManager();
    this.imageRetainingFragment = (ImageRetainingFragment) fragmentManager.findFragmentByTag(FRAGMENT_NAME);
    // create the fragment and bitmap the first time    
    if (this.imageRetainingFragment == null) {
        this.imageRetainingFragment = new ImageRetainingFragment();
        fragmentManager.beginTransaction()
                 // Add a fragment to the activity state.               
                .add(this.imageRetainingFragment, FRAGMENT_NAME)
                .commit();
    }
}

private void tryLoadImage() {
    if (this.imageRetainingFragment == null) {
        return;
    }

    Bitmap selectedImage = this.imageRetainingFragment.getImage();
    if (selectedImage == null) {
        return;
    }

    ImageView selectedImageView = (ImageView) findViewById(R.id.selectedImage);
    selectedImageView.setImageBitmap(selectedImage);
}