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:

 <? 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 >

<?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：

 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);

     }
 }

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。