package my.package;

class OffScreenView extends View {
   public OffScreenView(Context context, AttributeSet attrs) {
     super(context, attrs);
   }

   Bitmap buffer = null;
   Canvas offScreen = null;

   public void onDraw( Canvas c ) {
     if( buffer==null ) {
      buffer = Bitmap.createBitmap( c.getWidth(), c.getHeight(), Bitmap.Config.ARGB_8888 );
      offScreen = new Canvas(buffer);
     }
     c.drawBitmap(buffer,0,0,null);
   }

}

<my.package.OffScreenView
    android:layout_width="..."
    ...
   android:id="@+id/offscreen"
/>

class Updater implements Runnable {
  OffScreenView theView;
  boolean running;
  public Updater( OffScreenView theView ) { this.theView = theView; ... }
  public void run() {
     while( running ) {
        theView.postInvalidate();
        try { Thread.sleep( 1000 / FRAMERATE ); } catch( InterruptedException wont_care ) {}
     }
  }
}

....MyActivity...

   private Updater upd;

   public void onCreate( Bundle bundle ) {
     super.onCreate(nundle);
     upd = new Updater( (OffScreenView)findViewById(R.id.offscreen)) );
     ...
  }

   public void onResume() {
      super.onResume();
      new Thread(upd).start();
   }
      
   public void onPause() {
      super.onPause();
      upd.running = false;
   }

public void run() {
  while( running ) {
     long start = System.currentTimeMillis();
     .. neues bild aufbauen .. 
     long time = System.currentTimeMillis() - start;
     .. 1000 / FRAMERATE - time warten ..
    theView.postInvalidate();
  }