初学Android,图形图像之使用SurfaceView(三十九)

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SurfaceView支持双缓冲，在实现游戏绘图上面比View更出色

它有几个重要方法

Canvas lockCanvas():　锁定整个SurfaceView对象,获取该Surface上的Canvas

Canvas lockCanvas(Rect dirty):　锁定SurfaceView上Rect划分的区域，获取该Surface上的Canvas

unlockCanvasAndPost(canvas): 释放绘图，提交所绘制的class="tags" href="/tags/TuXing.html" title=图形>图形

SurfaceView的特性是，class="tags" href="/tags/TuXing.html" title=图形>图形可以覆盖显示，它控制了z轴的显示，后draw的class="tags" href="/tags/TuXing.html" title=图形>图形可以把先draw的class="tags" href="/tags/TuXing.html" title=图形>图形盖住

下面是示例效果

主界面放入一个SurfaceView

class="language-html"><?xml version="1.0" class="tags" href="/tags/ENCODING.html" title=encoding>encoding="utf-8"?>
<LinearLayout xmlns:class="tags" href="/tags/ANDROID.html" title=android>android="http://schemas.class="tags" href="/tags/ANDROID.html" title=android>android.com/apk/res/class="tags" href="/tags/ANDROID.html" title=android>android"
    class="tags" href="/tags/ANDROID.html" title=android>android:class="tags" href="/tags/LAYOUT.html" title=layout>layout_width="fill_parent"
    class="tags" href="/tags/ANDROID.html" title=android>android:class="tags" href="/tags/LAYOUT.html" title=layout>layout_height="fill_parent"
    class="tags" href="/tags/ANDROID.html" title=android>android:orientation="vertical" >

    <SurfaceView
        class="tags" href="/tags/ANDROID.html" title=android>android:id="@+id/show"
        class="tags" href="/tags/ANDROID.html" title=android>android:class="tags" href="/tags/LAYOUT.html" title=layout>layout_width="fill_parent"
        class="tags" href="/tags/ANDROID.html" title=android>android:class="tags" href="/tags/LAYOUT.html" title=layout>layout_height="fill_parent" />
</LinearLayout>

主界面drawclass="tags" href="/tags/TuXing.html" title=图形>图形的代码　

class="language-java">package org.crazyit.image;

import class="tags" href="/tags/ANDROID.html" title=android>android.app.Activity;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.Bitmap;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.BitmapFactory;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.Canvas;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.Color;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.Paint;
import class="tags" href="/tags/ANDROID.html" title=android>android.graphics.Rect;
import class="tags" href="/tags/ANDROID.html" title=android>android.os.Bundle;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.MotionEvent;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.SurfaceHolder;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.SurfaceHolder.Callback;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.SurfaceView;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.View;
import class="tags" href="/tags/ANDROID.html" title=android>android.view.View.OnTouchListener;

public class SurfaceViewTest extends Activity
{
	// SurfaceHolder负责维护SurfaceView上绘制的内容
	private SurfaceHolder holder;
	private Paint paint;
	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(R.class="tags" href="/tags/LAYOUT.html" title=layout>layout.main);
		paint = new Paint();	
		SurfaceView surface = (SurfaceView) findViewById(R.id.show);
		// 初始化SurfaceHolder对象
		holder = surface.getHolder();
		holder.addCallback(new Callback()
		{
			@Override
			public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2,
				int arg3)
			{
			}

			@Override
			public void surfaceCreated(SurfaceHolder holder)
			{
				// 锁定整个SurfaceView
				Canvas canvas = holder.lockCanvas();
				// 绘制背景
				Bitmap back = BitmapFactory.decodeResource(
					SurfaceViewTest.this.getResources(), R.drawable.sun);
				//绘制背景
				canvas.drawBitmap(back, 0, 0, null);
				// 绘制完成，释放画布，提交修改
				holder.unlockCanvasAndPost(canvas);
				//重新锁一次，"持久化"上次所绘制的内容
				holder.lockCanvas(new Rect(0, 0, 0, 0));
				holder.unlockCanvasAndPost(canvas);
			}

			@Override
			public void surfaceDestroyed(SurfaceHolder holder)
			{
			}
		});
		//为surface的触摸事件绑定监听器
		surface.setOnTouchListener(new OnTouchListener()
		{
			@Override
			public boolean onTouch(View source, MotionEvent event)
			{
				// 只处理按下事件
				if (event.getAction() == MotionEvent.ACTION_DOWN)
				{
					int cx = (int) event.getX();
					int cy = (int) event.getY();
					// 锁定SurfaceView的局部区域，只更新局部内容
					Canvas canvas = holder.lockCanvas(new Rect(cx - 50,
						cy - 50, cx + 50, cy + 50));
					// 保存canvas的当前状态
					canvas.save();
					// 旋转画布
					canvas.rotate(30, cx, cy);
					paint.setColor(Color.RED);
					// 绘制红色方块
					canvas.drawRect(cx - 40, cy - 40, cx, cy, paint);
					// 恢复Canvas之前的保存状态
					canvas.restore();
					paint.setColor(Color.GREEN);
					// 绘制绿色方块
					canvas.drawRect(cx, cy, cx + 40, cy + 40, paint);
					// 绘制完成，释放画布，提交修改
					holder.unlockCanvasAndPost(canvas);
				}
				return false;
			}
		});
	}
}