Can a custom View know that onPause has been called?

Question

I have a custom View that runs a Thread operation which sits around making calls to the interwebs periodically. I would like to know if there\'s a way for me to not have to kil

Answer 1

Yes you can. All that you need is to have a field of LifecycleOwner type. More about it in official documentation. In my case i created a custom view with another view from 3rd party library - CameraView.

At first, custom view needs to implement LifecycleOberver interface

public class MakePhotoView extends ConstraintLayout implements LifecycleObserver

So, i have a field in my custom view:

private LifecycleOwner mLifecycleOwner;

I pass it in the constructor as one of parameters:

public MakePhotoView(Context context, OnPhotoMadeListener onPhotoMadeListener, LifecycleOwner lifecycleOwner) {
    super(context);
    mOnPhotoMadeListener = onPhotoMadeListener;
    mLifecycleOwner = lifecycleOwner;
    init();
}

After that i register my custom view as observer for lifecycle events in LifecycleOwner:

private void init() {
    //other code
    mLifecycleOwner.getLifecycle().addObserver(this);
}

And finally i can listen for lifecycle events:

@OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
public void startCamera() {
    AppLog.logObject(this, "On Resume called for MakeCameraView");
    mCameraView.start();
}

@OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
public void stopCamera() {
    AppLog.logObject(this, "On Pause called for MakeCameraView");
    mCameraView.stop();
}

@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
public void destroyCamera() {
    AppLog.logObject(this, "On Destroy called for MakeCameraView");
    mCameraView.destroy();
}