Android canvas的save()和restore()用法-优快云博客

读Android SDK里面的samples里面游戏的时候，很多时候都看到对canvas的save()和restore()运用。

下面是个小程序，使用了这两个方面，使得旋转红色方块的时候，保证蓝色方块不受影响。

代码如下：

Java代码

packagecom.ray.test;
importandroid.app.Activity;
importandroid.content.Context;
importandroid.graphics.Canvas;
importandroid.graphics.Color;
importandroid.graphics.Paint;
importandroid.os.Bundle;
importandroid.view.SurfaceHolder;
importandroid.view.SurfaceView;
publicclassTestextendsActivity{
/**Calledwhentheactivityisfirstcreated.*/
@Override
publicvoidonCreate(BundlesavedInstanceState){
super.onCreate(savedInstanceState);
setContentView(newMyView(this));
}
classMyViewextendsSurfaceViewimplementsSurfaceHolder.Callback{
privateSurfaceHoldermHolder;
privateCanvascanvas;
publicMyView(Contextcontext){
super(context);
mHolder=getHolder();
mHolder.addCallback(this);
}
@Override
publicvoidsurfaceChanged(SurfaceHolderholder,intformat,intwidth,
intheight){
}
@Override
publicvoidsurfaceCreated(SurfaceHolderholder){
canvas=mHolder.lockCanvas();
PaintmPaint=newPaint();
mPaint.setColor(Color.BLUE);
canvas.drawRect(100,200,200,300,mPaint);
canvas.save();
canvas.rotate(45);
mPaint.setColor(Color.RED);
canvas.drawRect(150,10,200,60,mPaint);
canvas.restore();
mHolder.unlockCanvasAndPost(canvas);
}
@Override
publicvoidsurfaceDestroyed(SurfaceHolderholder){
//TODOAuto-generatedmethodstub
}
}
}

package com.ray.test;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class Test extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new MyView(this));
    }
    
    class MyView extends SurfaceView implements SurfaceHolder.Callback{

    	private SurfaceHolder mHolder;
    	private Canvas canvas;
		public MyView(Context context) {
			super(context);
			mHolder = getHolder();
			mHolder.addCallback(this);
		}
		
		@Override
		public void surfaceChanged(SurfaceHolder holder, int format, int width,
				int height) {
			
		}

		@Override
		public void surfaceCreated(SurfaceHolder holder) {
			canvas = mHolder.lockCanvas();
			Paint mPaint = new Paint();
			mPaint.setColor(Color.BLUE);
			canvas.drawRect(100, 200, 200, 300, mPaint);
			
			canvas.save();
			canvas.rotate(45);
			mPaint.setColor(Color.RED);
			canvas.drawRect(150, 10, 200, 60, mPaint);
			canvas.restore();
			mHolder.unlockCanvasAndPost(canvas);
		}

		@Override
		public void surfaceDestroyed(SurfaceHolder holder) {
			// TODO Auto-generated method stub
			
		}
    	
    }
}

Test.rar (24.1 KB)