Loader animation using Custom View in Android

Question

I created a loader animation for an Android app: a simple 3 dots loader.

Is this the correct way to animate by using TimerTask?

public class ThreeDotsLoader extends View {
 Paint dot1;
 Paint dot2;
 Paint dot3;
 int defaultColor;
 int highlightColor;
 boolean animationStarted = false;
 TimerTask task;
 Timer timer;
 int count = 1;
 public ThreeDotsLoader(Context context, AttributeSet attrs) {
 super(context, attrs);
 defaultColor = Color.rgb(44, 78, 82);
 highlightColor = Color.WHITE;
 initPaint();
 }
 @Override
 protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 Log.d("custom", "ondraw");
 canvas.drawCircle(50, 50, 15, dot1);
 canvas.drawCircle(100, 50, 15, dot2);
 canvas.drawCircle(150, 50, 15, dot3);
 }
 private void initPaint(){
 dot1 = new Paint();
 dot1.setColor(defaultColor);
 dot1.setStyle(Paint.Style.FILL);
 dot1.setAntiAlias(true);
 dot2 = new Paint();
 dot2.setColor(defaultColor);
 dot2.setStyle(Paint.Style.FILL);
 dot2.setAntiAlias(true);
 dot3 = new Paint();
 dot3.setColor(defaultColor);
 dot3.setStyle(Paint.Style.FILL);
 dot3.setAntiAlias(true);
 }
 public void startLoading(){
 task = new TimerTask() {
 @Override
 public void run() {
 switch(count){
 case 1:
 dot1.setColor(highlightColor);
 dot2.setColor(defaultColor);
 dot3.setColor(defaultColor);
 count++;
 break;
 case 2:
 dot1.setColor(defaultColor);
 dot2.setColor(highlightColor);
 dot3.setColor(defaultColor);
 count++;
 break;
 case 3:
 dot1.setColor(defaultColor);
 dot2.setColor(defaultColor);
 dot3.setColor(highlightColor);
 count = 1;
 break;
 }
 animationStarted = true;
 postInvalidate();
 }
 };
 timer = new Timer();
 timer.schedule(task, 0, 300);
 }
 public void stopLoading(){
 animationStarted = false;
 timer.cancel();
 }
}

Answer 1

I would avoid "new Timer();" for this use case. The timer task it changing the paint object on a thread other than the main UI thread, which is very likely to lead to non-deterministic behavior.

I recommend using an ObjectAnimator ( see the Property animation guide )

If you need to support pre-API 11 releases, you can use NineOldAndroids.