Double buffering technology realizes the application _android of Android artboard

What is double buffering technology? Double buffering technology is when the user interface is complete, there will be a buffer to save the results of user operations.

Why use double buffering technology? Take the development of Android games, the interface is all repaint each time, also said to draw a new, the old is gone, so need to use double buffer technology to save the previous content.

How to achieve double buffering? Use a Bitmap object to retain the previous canvas.

Package com.example.phonegaptest; 
Import Android.content.Context; 
Import Android.graphics.Bitmap; 
Import Android.graphics.Bitmap.Config; 
Import Android.graphics.Canvas; 
Import Android.graphics.Color; 
Import Android.graphics.Paint; 
Import Android.graphics.Path; 
Import Android.util.AttributeSet; 
Import android.view.MotionEvent; 
 
Import Android.view.View; 
 public class Drawview extends View {float PreX; 
 float prey; 
 private path Path; 
 Public Paint Paint = null; 
 Final int view_width = 320; 
 Final int view_height = 480; 
 Bitmap cachebitmap = null; 
 
 Canvas Cachecanvas = null; 
  Public Drawview (context, AttributeSet set) {Super (context, set); 
  Cachebitmap = Bitmap.createbitmap (View_width, View_height, config.argb_8888); 
 
  Cachecanvas = new Canvas (); 
  Path = new Path (); 
 
  Cachecanvas.setbitmap (CACHEBITMAP); 
  Paint = new Paint (Paint.dither_flag); 
  Paint.setcolor (color.red); 
  Paint.setstyle (Paint.Style.STROKE); Paint.setstrokewidth(1); 
  Paint.setantialias (TRUE); 
 Paint.setdither (TRUE); 
  @Override public boolean ontouchevent (Motionevent event) {float x = Event.getx (); 
 
  Float y = event.gety (); 
   Switch (event.getaction ()) {case MotionEvent.ACTION_DOWN:path.moveTo (x, y); 
   PreX = x; 
   Prey = y; 
  Break 
   Case MotionEvent.ACTION_MOVE:path.quadTo (PreX, Prey, x, y); 
   PreX = x; 
   Prey = y; 
  Break 
   Case MotionEvent.ACTION_UP:cacheCanvas.drawPath (path, paint); 
   Path.reset (); 
  Break 
  } invalidate (); 
 return true; 
  } @Override protected void OnDraw (Canvas Canvas) {Super.ondraw (Canvas); 
  Paint bmppaint = new Paint (); 
  Canvas.drawbitmap (cachebitmap, 0, 0, bmppaint); 
 Canvas.drawpath (path, paint);  } 
 
}

Above is the Android double buffering technology implementation of the artboard application example, the need for friends can refer to.