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java – Android Animation: Wait until finished?

Posted by: admin April 23, 2020 Leave a comment

Questions:

I would like to wait until an animation is finished* in an Android ImageView before continuing program execution, what is the proper way to do this?

  • (in this context “finished” means that it runs through all of its frames exactly one time and stops on the last one. I am unclear whether this animation will be an android:oneshot=”true” animation because I will be using it multiple times, but it will not be run continuously but intermittently)

Research/Guesses:

A. At heart my question seems to be a Java thread question because the Android AnimationDrawable implements Java.lang.Runnable. So maybe threads are the solution. Perhaps the answer will include join?

B. The approach of others seems to have been to use AnimationListener, this seems difficult and needlessly complex for my simple needs. Plus I’m not exactly sure how to do it.

C. The AnimationDrawable class has a (boolean) isRunning method which could probably be used in a while loop (i.e. while(anim.isRunning()){wait(100ms)}). But I have a gut feeling that this is the wrong approach. Although something similar seems to be mentioned in the concurrency tutorial

Code Snippet

   this.q_pic_view.setImageResource(0);
    this.q_pic_view.setBackgroundResource(R.drawable.animation_test);
    AnimationDrawable correct_animation = (AnimationDrawable) this.q_pic_view.getBackground();
    correct_animation.start();

    //here I tried to implement option C but it didn't work
    while(correct_animation.isRunning()){
        try {
           Thread.sleep(20);
        } catch (InterruptedException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
        }
    }

Animation

<?xml version="1.0" encoding="utf-8"?>
<animation-list android:id="@+id/AnimTest" android:oneshot="true" xmlns:android="http://schemas.android.com/apk/res/android">
  <item android:drawable="@drawable/animtest001" android:duration="33"/>
  <item android:drawable="@drawable/animtest002" android:duration="100"/>
  <item android:drawable="@drawable/animtest003" android:duration="66"/>
  <item android:drawable="@drawable/animtest004" android:duration="66"/>
  <item android:drawable="@drawable/animtest005" android:duration="33"/>
  <item android:drawable="@drawable/animtest006" android:duration="66"/>
  <item android:drawable="@drawable/animtest007" android:duration="33"/>
  <item android:drawable="@drawable/animtest008" android:duration="66"/>
  <item android:drawable="@drawable/animtest009" android:duration="100"/>
  <item android:drawable="@drawable/animtest010" android:duration="100"/>
</animation-list>

One Possible way to achieve the desired effect, though not an answer to my question, is to delay the execution of further code by doing something like this:

int duration = 0;
//Add all of the frames together
for (int i=0; i<my_animation.getNumberOfFrames(); i++){
    duration = duration + correct_animation.getDuration(i);
    }
//delay the execution 
Handler handler = new Handler();
handler.postDelayed(new Runnable(){
    public void run() {
       DoYourNextStuff();
        }
}, duration); //delay is here

Edit: There are many ways to solve this problem, the answer given probably does solve the problem I didn’t test it, but I ended up just waiting the correct amount of time (at first), then I changed to using an async task (which has a handler method for completion) and ran my animation in the updateProgress call of the async task directly. In the last iteration I am using a threaded surface view to run the animation. This last way is by far the fastest and best (for reasons other then those asked about in this post). I hope it helps someone.

How to&Answers:

Suggest you

  • Create an object to encapsulate the “animation” lifetime
  • In the object, you’ll have a thread OR a Timer
  • Provide methods to start() the animation and awaitCompletion()
  • Use a private final Object completionMonitor field to track completion, synchronize on it, and use wait() and notifyAll() to coordinate the awaitCompletion()

Code snippet:

final class Animation {

    final Thread animator;

    public Animation()
    {
      animator = new Thread(new Runnable() {
        // logic to make animation happen
       });

    }

    public void startAnimation()
    {
      animator.start();
    }

    public void awaitCompletion() throws InterruptedException
    {
      animator.join();
    }
}

You could also use a ThreadPoolExecutor with a single thread or ScheduledThreadPoolExecutor, and capture each frame of the animation as a Callable. Submitting the sequence of Callables and using invokeAll() or a CompletionService to block your interested thread until the animation is complete.

Answer:

The easiest way would be to post a (delayed) Runnable to the UI thread:

Animation fadeout = new AlphaAnimation(1.f, 0.f);
fadeout.setDuration(500);
view.startAnimation(fadeout);
view.postDelayed(new Runnable() {
    @Override
    public void run() {
        view.setVisibility(View.GONE);
    }
}, 500);

That will do the job painlessly. And never (never, never, never!) try to block the UI thread in Android. If you did so, the phone freezes and you would not see the animation anyway.
If you need to wait some time, use another thread.

Answer:

Use the Animation listener to listen to animation lifecycle hooks.

Animation fadeout = new AlphaAnimation(1.f, 0.f);
fadeout.setDuration(500);    
final View viewToAnimate = view;
fadeout.setAnimationListener(new AnimationListener(){

   @Override
   public void onAnimationStart(Animation animation){}

   @Override
   public void onAnimationRepeat(Animation animation){}

   @Override
   public void onAnimationEnd(Animation animation){
       viewToAnimate.setVisibility(View.GONE);
   }
});
view.startAnimation(fadeout);

Answer:

Hi another alternatives is using ObjectAnimator. Again as others mentioned you would have to use a Listner

//get an image resource    
ImageView imgView = (ImageView) findViewById(R.id.some_image);      
//create and init an ObjectAnimator  
ObjectAnimator animation;
animation = ObjectAnimator.ofFloat(imgView, "rotationY", 0.0f, 360f);

//set the duration of each iteration
animation.setDuration(1500);
//set number of iterations
animation.setRepeatCount(1);
//set setInterpolator 

animation.setInterpolator(new AccelerateDecelerateInterpolator());
//Add a listner to check when the animation ends
animation.addListener(new AnimatorListenerAdapter() {
       @Override
       public void onAnimationEnd(Animator animation) {
                //postFirstAnimation(): This function is called after the animation ends
                postFirstAnimation();
       }
});
//start the animation
animation.start();