Android提高第二篇之SurfaceView的基本使用

本文来自http://blog.csdn.net/hellogv/ ，引用必须注明出处！

上次介绍MediaPlayer的时候略微介绍了SurfaceView，SurfaceView因为能够直接从内存或者DMA等硬件接口取得图像数据，因此是个非常重要的画图容器，这次我就用两篇文章来介绍SurfaceView的使用方法。网上介绍SurfaceView的使用方法有非常多，写法也层出不同，比如继承SurfaceView类，或者继承SurfaceHolder.Callback类等，这个能够依据功能实际须要自己选择，我这里就直接在普通的用户界面调用SurfaceHolder的lockCanvas和unlockCanvasAndPost。

先来看看程序执行的截图：

截图1主要演示了直接把正弦波绘画在SurfaceView上

对照上面的左右两图，右图用.lockCanvas(null)，而左图用.lockCanvas(new Rect(oldX, 0, oldX + length,
    getWindowManager().getDefaultDisplay().getHeight()))，对照一下两个效果，因为左图是按指定Rect绘画，所以效率会比右图的全控件绘画高些，而且在清屏之后(canvas.drawColor(Color.BLACK))不会留有上次绘画的残留。

接下来贴出main.xml的源代码:

<?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>

接下来贴出程序源代码：

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) {//假设到了终点，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内降低循环画线的次数，能够提高画图效率。