Android SurfaceView 的应用

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，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。

对比下面的第二、三两图，三图用.lockCanvas(null)，而二图用.lockCanvas(new Rect(oldX, 0, oldX + length, getWindowManager().getDefaultDisplay().getHeight()))，对比一下两个效果，由于二图是按指定Rect绘画，所以效率会比三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。

main.xml

<?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>

TestSurfaceView.java

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@Overridepublic 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 {@Overridepublic 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 {@Overridepublic 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);}
}

http://www.oschina.net/code/snippet_54100_1423

转载于:https://www.cnblogs.com/jqyp/archive/2012/01/01/2309682.html