package org.anddev.android.bouncingball;

import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.os.Handler;
import android.os.Message;

public class BounceActivity extends Activity {

     // Just a RANDOM ID to recognize a Message later
     protected static final int GUIUPDATEIDENTIFIER = 0x101;

     Thread myRefreshThread = null;

     /* Our 'ball' is located within this View */
     BounceView myBounceView = null;

     Handler myGUIUpdateHandler = new Handler() {

          // @Override
          public void handleMessage(Message msg) {
               switch (msg.what) {
                    case BounceActivity.GUIUPDATEIDENTIFIER:
                         /* Repaint the BounceView
                          * (where the ball is in) */
                         myBounceView.invalidate();
                         break;
               }
               super.handleMessage(msg);
          }
     };

     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle icicle) {
          super.onCreate(icicle);
          // Set fullscreen
          this.requestWindowFeature(Window.FEATURE_NO_TITLE);

          // Create a
          this.myBounceView = new BounceView(this);
          this.setContentView(this.myBounceView);

          /* create a Thread that will
           * periodically send messages
           * to our Handler */
          new Thread(new RefreshRunner()).start();
     }

     class RefreshRunner implements Runnable {
          // @Override
          public void run() {
               while (!Thread.currentThread().isInterrupted()) {
                    // Send Message to the Handler which will call the invalidate() method of the BOucneView
                    Message message = new Message();
                    message.what = BounceActivity.GUIUPDATEIDENTIFIER;
                    BounceActivity.this.myGUIUpdateHandler.sendMessage(message);

                    try {
                         Thread.sleep(100); // a 10th of a second
                    } catch (InterruptedException e) {
                         Thread.currentThread().interrupt();
                    }
               }
          }
     }
}

package org.anddev.android.bouncingball;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Point;
import android.graphics.drawable.Drawable;
import android.view.View;

public class BounceView extends View {

     /* Our Ball together with the location it will be painted*/
     protected Drawable mySprite;
     protected Point mySpritePos = new Point(0,0);
     
     /* Working with a Enum is 10000%
      * safer than working with int's
      * to 'remember' the direction. */
     protected enum HorizontalDirection {LEFT, RIGHT}
     protected enum VerticalDirection {UP, DOWN}
     protected HorizontalDirection myXDirection = HorizontalDirection.RIGHT;
     protected VerticalDirection myYDirection = VerticalDirection.UP;


     public BounceView(Context context) {
          super(context);
          // Set the background
          this.setBackground(this.getResources().getDrawable(R.drawable.icon));
          // Load our "Ball"
          this.mySprite = this.getResources().getDrawable(R.drawable.icon);
     }

     @Override
     protected void onDraw(Canvas canvas) {
          /* Check if the Ball started to leave
           * the screen on left or right side */
          if (mySpritePos.x >= this.getWidth() - mySprite.getBounds().width()) {
               this.myXDirection = HorizontalDirection.LEFT;
          } else if (mySpritePos.x <= 0) {
               this.myXDirection = HorizontalDirection.RIGHT;
          }

          /* Check if the Ball started to leave
           * the screen on bottom or upper side */
          if (mySpritePos.y >= this.getHeight() - mySprite.getBounds().height()) {
               this.myYDirection = VerticalDirection.UP;
          } else if (mySpritePos.y <= 0) {
               this.myYDirection = VerticalDirection.DOWN;
          }

          /* Move the ball left or right */
          if (this.myXDirection == HorizontalDirection.RIGHT) {
               this.mySpritePos.x += 10;
          } else {
               this.mySpritePos.x -= 10;
          }
          /* Move the ball up or down */
          if (this.myYDirection == VerticalDirection.DOWN) {
               this.mySpritePos.y += 10;
          } else {
               this.mySpritePos.y -= 10;
          }

          /* Set the location, where the sprite
           * will draw itself to the canvas */
          this.mySprite.setBounds(this.mySpritePos.x, this.mySpritePos.y,
                    this.mySpritePos.x + 50, this.mySpritePos.y + 50);
          
          /* Make the sprite draw itself to the canvas */
          this.mySprite.draw(canvas);
     }
}