Android提高第二篇之SurfaceView(上)

上次介绍MediaPlayer 的 时候稍微介绍了SurfaceView，SurfaceView由于可以直接从内存或者DMA等硬件接口取得图像数据，因此是个非常重要的绘图容器，这次 我就用两篇文章来介绍SurfaceView的用法。网上介绍SurfaceView的用法有很多，写法也层出不同，例如继承SurfaceView类， 或者继承SurfaceHolder.Callback类等，这个可以根据功能实际需要自己选择，我这里就直接在普通的用户界面调用 SurfaceHolder的lockCanvas和unlockCanvasAndPost。

        先来看看程序运行的截图：

截图1主要演示了直接把正弦波绘画在SurfaceView上

对比上面的左右两图，右图用.lockCanvas(null)，而左图用.lockCanvas(new Rect(oldX, 0, oldX + length,
    getWindowManager().getDefaultDisplay().getHeight()))， 对比一下两个效果，由于左图是按指定Rect绘画，所以效率会比右图的全控件绘画高些，并且在清屏之后 (canvas.drawColor(Color.BLACK))不会留有上次绘画的残留。

 

接下来贴出main.xml的源码:

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1. <? xml   version = "1.0"   encoding = "utf-8" ?>   
2. < LinearLayout   xmlns:android = "http://schemas.android.com/apk/res/android"   
3.     android:layout_width = "fill_parent"   android:layout_height = "fill_parent"   
4.     android:orientation = "vertical" >   
5.   
6.     < LinearLayout   android:id = "@+id/LinearLayout01"   
7.         android:layout_width = "wrap_content"   android:layout_height = "wrap_content" >   
8.         < Button   android:id = "@+id/Button01"   android:layout_width = "wrap_content"   
9.             android:layout_height = "wrap_content"   android:text = "简单绘画" > </ Button >   
10.         < Button   android:id = "@+id/Button02"   android:layout_width = "wrap_content"   
11.             android:layout_height = "wrap_content"   android:text = "定时器绘画" > </ Button >   
12.     </ LinearLayout >   
13.     < SurfaceView   android:id = "@+id/SurfaceView01"   
14.         android:layout_width = "fill_parent"   android:layout_height = "fill_parent" > </ SurfaceView >   
15. </ LinearLayout >   

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical"> <LinearLayout android:id="@+id/LinearLayout01" android:layout_width="wrap_content" android:layout_height="wrap_content"> <Button android:id="@+id/Button01" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="简单绘画"></Button> <Button android:id="@+id/Button02" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="定时器绘画"></Button> </LinearLayout> <SurfaceView android:id="@+id/SurfaceView01" android:layout_width="fill_parent" android:layout_height="fill_parent"></SurfaceView> </LinearLayout>

接下来贴出程序源码：

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1. package  com.testSurfaceView;  
2.   
3. import  java.util.Timer;  
4. import  java.util.TimerTask;  
5.   
6. import  android.app.Activity;  
7. import  android.graphics.Canvas;  
8. import  android.graphics.Color;  
9. import  android.graphics.Paint;  
10. import  android.graphics.Rect;  
11. import  android.os.Bundle;  
12. import  android.util.Log;  
13. import  android.view.SurfaceHolder;  
14. import  android.view.SurfaceView;  
15. import  android.view.View;  
16. import  android.widget.Button;  
17.   
18. public   class  testSurfaceView  extends  Activity {  
19.     /** Called when the activity is first created. */   
20.     Button btnSimpleDraw, btnTimerDraw;  
21.     SurfaceView sfv;  
22.     SurfaceHolder sfh;  
23.   
24.     private  Timer mTimer;  
25.     private  MyTimerTask mTimerTask;  
26.     int  Y_axis[], //保存正弦波的Y轴上的点   
27.     centerY,//中心线   
28.     oldX,oldY,//上一个XY点    
29.     currentX;//当前绘制到的X轴上的点   
30.   
31.     @Override   
32.     public   void  onCreate(Bundle savedInstanceState) {  
33.         super .onCreate(savedInstanceState);  
34.         setContentView(R.layout.main);  
35.   
36.         btnSimpleDraw = (Button) this .findViewById(R.id.Button01);  
37.         btnTimerDraw = (Button) this .findViewById(R.id.Button02);  
38.         btnSimpleDraw.setOnClickListener(new  ClickEvent());  
39.         btnTimerDraw.setOnClickListener(new  ClickEvent());  
40.         sfv = (SurfaceView) this .findViewById(R.id.SurfaceView01);  
41.         sfh = sfv.getHolder();  
42.   
43.         //动态绘制正弦波的定时器   
44.         mTimer = new  Timer();  
45.         mTimerTask = new  MyTimerTask();  
46.   
47.         // 初始化y轴数据   
48.         centerY = (getWindowManager().getDefaultDisplay().getHeight() - sfv  
49.                 .getTop()) / 2 ;  
50.         Y_axis = new   int [getWindowManager().getDefaultDisplay().getWidth()];  
51.         for  ( int  i =  1 ; i < Y_axis.length; i++) { // 计算正弦波   
52.             Y_axis[i - 1 ] = centerY  
53.                     - (int ) ( 100  * Math.sin(i *  2  * Math.PI /  180 ));  
54.         }  
55.     }  
56.   
57.     class  ClickEvent  implements  View.OnClickListener {  
58.   
59.         @Override   
60.         public   void  onClick(View v) {  
61.   
62.             if  (v == btnSimpleDraw) {  
63.                 SimpleDraw(Y_axis.length-1 ); //直接绘制正弦波   
64.               
65.             } else   if  (v == btnTimerDraw) {  
66.                 oldY = centerY;  
67.                 mTimer.schedule(mTimerTask, 0 ,  5 ); //动态绘制正弦波   
68.             }  
69.   
70.         }  
71.   
72.     }  
73.   
74.     class  MyTimerTask  extends  TimerTask {  
75.         @Override   
76.         public   void  run() {  
77.   
78.             SimpleDraw(currentX);  
79.             currentX++;//往前进   
80.             if  (currentX == Y_axis.length -  1 ) { //如果到了终点，则清屏重来   
81.                 ClearDraw();  
82.                 currentX = 0 ;  
83.                 oldY = centerY;  
84.             }  
85.         }  
86.   
87.     }  
88.       
89.     /*  
90.      * 绘制指定区域  
91.      */   
92.     void  SimpleDraw( int  length) {  
93.         if  (length ==  0 )  
94.             oldX = 0 ;  
95.         Canvas canvas = sfh.lockCanvas(new  Rect(oldX,  0 , oldX + length,  
96.                 getWindowManager().getDefaultDisplay().getHeight()));// 关键:获取画布   
97.         Log.i("Canvas:" ,  
98.                 String.valueOf(oldX) + ","  + String.valueOf(oldX + length));  
99.   
100.         Paint mPaint = new  Paint();  
101.         mPaint.setColor(Color.GREEN);// 画笔为绿色   
102.         mPaint.setStrokeWidth(2 ); // 设置画笔粗细   
103.   
104.         int  y;  
105.         for  ( int  i = oldX +  1 ; i < length; i++) { // 绘画正弦波   
106.             y = Y_axis[i - 1 ];  
107.             canvas.drawLine(oldX, oldY, i, y, mPaint);  
108.             oldX = i;  
109.             oldY = y;  
110.         }  
111.         sfh.unlockCanvasAndPost(canvas);// 解锁画布，提交画好的图像   
112.     }  
113.   
114.     void  ClearDraw() {  
115.         Canvas canvas = sfh.lockCanvas(null );  
116.         canvas.drawColor(Color.BLACK);// 清除画布   
117.         sfh.unlockCanvasAndPost(canvas);  
118.   
119.     }  
120. }  

package com.testSurfaceView; import java.util.Timer; import java.util.TimerTask; import android.app.Activity; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Rect; import android.os.Bundle; import android.util.Log; import android.view.SurfaceHolder; import android.view.SurfaceView; import android.view.View; import android.widget.Button; public class testSurfaceView extends Activity { /** Called when the activity is first created. */ Button btnSimpleDraw, btnTimerDraw; SurfaceView sfv; SurfaceHolder sfh; private Timer mTimer; private MyTimerTask mTimerTask; int Y_axis[],//保存正弦波的Y轴上的点 centerY,//中心线 oldX,oldY,//上一个XY点 currentX;//当前绘制到的X轴上的点 @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); btnSimpleDraw = (Button) this.findViewById(R.id.Button01); btnTimerDraw = (Button) this.findViewById(R.id.Button02); btnSimpleDraw.setOnClickListener(new ClickEvent()); btnTimerDraw.setOnClickListener(new ClickEvent()); sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01); sfh = sfv.getHolder(); //动态绘制正弦波的定时器 mTimer = new Timer(); mTimerTask = new MyTimerTask(); // 初始化y轴数据 centerY = (getWindowManager().getDefaultDisplay().getHeight() - sfv .getTop()) / 2; Y_axis = new int[getWindowManager().getDefaultDisplay().getWidth()]; for (int i = 1; i < Y_axis.length; i++) {// 计算正弦波 Y_axis[i - 1] = centerY - (int) (100 * Math.sin(i * 2 * Math.PI / 180)); } } class ClickEvent implements View.OnClickListener { @Override public void onClick(View v) { if (v == btnSimpleDraw) { SimpleDraw(Y_axis.length-1);//直接绘制正弦波 } else if (v == btnTimerDraw) { oldY = centerY; mTimer.schedule(mTimerTask, 0, 5);//动态绘制正弦波 } } } class MyTimerTask extends TimerTask { @Override public void run() { SimpleDraw(currentX); currentX++;//往前进 if (currentX == Y_axis.length - 1) {//如果到了终点，则清屏重来 ClearDraw(); currentX = 0; oldY = centerY; } } } /* * 绘制指定区域 */ void SimpleDraw(int length) { if (length == 0) oldX = 0; Canvas canvas = sfh.lockCanvas(new Rect(oldX, 0, oldX + length, getWindowManager().getDefaultDisplay().getHeight()));// 关键:获取画布 Log.i("Canvas:", String.valueOf(oldX) + "," + String.valueOf(oldX + length)); Paint mPaint = new Paint(); mPaint.setColor(Color.GREEN);// 画笔为绿色 mPaint.setStrokeWidth(2);// 设置画笔粗细 int y; for (int i = oldX + 1; i < length; i++) {// 绘画正弦波 y = Y_axis[i - 1]; canvas.drawLine(oldX, oldY, i, y, mPaint); oldX = i; oldY = y; } sfh.unlockCanvasAndPost(canvas);// 解锁画布，提交画好的图像 } void ClearDraw() { Canvas canvas = sfh.lockCanvas(null); canvas.drawColor(Color.BLACK);// 清除画布 sfh.unlockCanvasAndPost(canvas); } }

注意一下 for (int i = oldX + 1; i < length; i++) {// 绘画正弦波 这句，在.lockCanvas()指定Rect内减少循环画线的次数，可以提高绘图效率。