Android双缓冲绘图 Bitmap和Canvas 一看就懂

来源：互联网发布：人人商城分销系统源码编辑：程序博客网时间：2024/05/21 09:54

Android双缓冲绘图 Bitmap和Canvas

双缓冲是一种在内存中保留屏幕的副本或缓存的技术，先将所有图形都加载在内存中，然后一起绘制到屏幕上，避免了直接在屏幕上绘图时出现的明显闪烁。

实现步骤如下

定义：

Canvas bufferCanvas;

Bitmap bufferBitmap;

创建对象：

bufferCanvas=new Canvas(bufferBitmap);

在缓存中绘图：

bufferCanvas.drawCircle(x,y,radius,paint);

在屏幕上绘图：

canvas.drawBitmap(bufferBitmap,0,0,new Paint());

下面示例：使用双缓冲技术在屏幕上随机绘制500个不同半径的圆.

package graphics;import java.util.Random;import android.app.Activity;import android.content.Context;import android.graphics.Bitmap;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Point;import android.os.Bundle;import android.util.DisplayMetrics;import android.util.Log;import android.view.View;import android.view.Window;public class BitmapActivity extends Activity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);this.requestWindowFeature(Window.FEATURE_NO_TITLE);this.setContentView(new DrawView(this));}public class DrawView extends View {Bitmap bufferBitmap;Canvas bufferCanvas;Point screenSize;Random rand = new Random();public DrawView(Context context) {super(context);DisplayMetrics metrics = new DisplayMetrics();getWindowManager().getDefaultDisplay().getMetrics(metrics);screenSize = new Point(metrics.widthPixels - 20,metrics.heightPixels - 20);bufferBitmap = Bitmap.createBitmap(this.screenSize.x,this.screenSize.y, Bitmap.Config.ARGB_8888);//创建内存位图bufferCanvas = new Canvas(bufferBitmap);//创建绘图画布}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);drawOnBuffer();canvas.drawBitmap(bufferBitmap, 0, 0,new Paint());//在双缓冲中绘图，将自定义缓冲绘制到屏幕上}private void drawOnBuffer() {Paint paint=new Paint();paint.setAntiAlias(true);bufferCanvas.drawColor(Color.WHITE);for(int n=0;n<500;n++){                     //随机在绘图画布上绘制500个圆int r=rand.nextInt(256);int g=rand.nextInt(256);int b=rand.nextInt(256);paint.setColor(Color.rgb(r, g, b));int x=rand.nextInt(bufferCanvas.getWidth());int y=rand.nextInt(bufferCanvas.getHeight());int radius=rand.nextInt(100)+20;bufferCanvas.drawCircle(x, y, radius, paint);Log.d("Circle", "第n个"+n);}}}}

0 0