A simple problem with Android animations

Question

I am trying to implement a stream with some simple android animation. I just get a sleep error () - He says I need a method for this. I know that there is probably an obvious solution. My application just puts a ball that moves in a circle in a random place. I want to keep placing shapes in random places. In any case, can someone please tell me what I am doing wrong with my thread? Thanks.

public class DrawingTheBall extends View { Bitmap bball; Random randX, randY; double theta; Handler m_handler; Runnable m_handlerTask; //for some reason I get a syntax error here m_handler = new Handler(); public DrawingTheBall(Context context) { super(context); // TODO Auto-generated constructor stub bball = BitmapFactory.decodeResource(getResources(), R.drawable.blueball); //randX = 1 + (int)(Math.random()*500); //randY = 1 + (int)(Math.random()*500); randX = new Random(); randY = new Random(); theta = 45; new Thread(this).start(); } public void onDraw(Canvas canvas){ super.onDraw(canvas); //Radius, angle, and coordinates for circle motion float a = 50; float b = 50; float r = 50; int x = 0; int y = 0; theta = theta + Math.toRadians(2); //move ball in circle if(x < canvas.getWidth()){ x = randX.nextInt() + (int) (a +r*Math.cos(theta)); }else{ x = 0; } if(y < canvas.getHeight()){ y = randY.nextInt() + (int) (b +r*Math.sin(theta)); }else{ y = 0; } Paint p = new Paint(); } m_handlerTask = new Runnable() { @Override public void run() { // do something m_handler.postDelayed(m_handlerTask, 1000); invalidate(); } }; m_handlerTask.run(); 

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Answer 1

If you implement Thread or HandlerThread, make sure that the user interface thread does not block while waiting for the workflow to complete - do not call Thread.wait() or Thread.sleep() .

http://developer.android.com/training/articles/perf-anr.html

Instead of blocking while waiting for the workflow to complete, your main thread should provide a Handler for the rest of the threads, which will be sent back after completion.

Using a Handler

  Handler m_handler; Runnable m_handlerTask ; m_handler = new Handler(); m_handlerTask = new Runnable() { @Override public void run() { // do something m_handler.postDelayed(m_handlerTask, 1000); // instad of 1000 mention the delay in milliseconds } }; m_handlerTask.run(); 

When you need to cancel the handler, use m_handler.removeCallbacks (m_handlerTask);

Example:

  public class MainActivity extends Activity { RelativeLayout rl; int x = 0,y=0; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); rl = (RelativeLayout) findViewById(R.id.rl); CustomView cv = new CustomView(this); rl.addView(cv); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } public class CustomView extends View { Bitmap bball; Random randX, randY; double theta; Handler m_handler; Paint p ; int width; int height; Runnable m_handlerTask; public CustomView(Context context) { super(context); // TODO Auto-generated constructor stub p= new Paint(); bball = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher); //randX = 1 + (int)(Math.random()*500); //randY = 1 + (int)(Math.random()*500); randX = new Random(); randY = new Random(); theta = 45; m_handler = new Handler(); } @Override protected void onSizeChanged(int w, int h, int oldw, int oldh) { // TODO Auto-generated method stub super.onSizeChanged(w, h, oldw, oldh); width =w; height=h; } public void move() { m_handlerTask = new Runnable() { @Override public void run() { //theta = theta + Math.toRadians(2); if(x<300) { x= x+10; invalidate(); } else if(x>300) { x=0; m_handler.removeCallbacks(m_handlerTask); } // canvas.drawBitmap(bball, x, y, p); m_handler.postDelayed(m_handlerTask, 3000); } }; m_handlerTask.run(); } public void onDraw(final Canvas canvas){ super.onDraw(canvas); canvas.drawBitmap(bball, x, y, p); if(x<300) { move(); } else { m_handler.removeCallbacks(m_handlerTask); } } } }