Using double buffering technology to realize the application of Android artboard

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 Android game development, 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 do I implement 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 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);

}

}