Android SurfaceView 的基本应用

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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。

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[图片] 程序运行的截图

[图片] 1.gif

[图片] 2.gif

[代码] main.xml

01

02

03	android:layout_width="fill_parent" android:layout_height="fill_parent"

04	android:orientation="vertical">

05

06

07	android:layout_width="wrap_content" android:layout_height="wrap_content">

08

09	android:layout_height="wrap_content" android:text="简单绘画">

10

11	android:layout_height="wrap_content" android:text="定时器绘画">

12

13

14	android:layout_width="fill_parent" android:layout_height="fill_parent">

15

[代码] TestSurfaceView.java

001	package com.testSurfaceView;

002

003	import java.util.Timer;

004	import java.util.TimerTask;

005

006	import android.app.Activity;

007	import android.graphics.Canvas;

008	import android.graphics.Color;

009	import android.graphics.Paint;

010	import android.graphics.Rect;

011	import android.os.Bundle;

012	import android.util.Log;

013	import android.view.SurfaceHolder;

014	import android.view.SurfaceView;

015	import android.view.View;

016	import android.widget.Button;

017

018	public class TestSurfaceView extends Activity {

019	/** Called when the activity is first created. */

020	Button btnSimpleDraw, btnTimerDraw;

021	SurfaceView sfv;

022	SurfaceHolder sfh;

023

024	private Timer mTimer;

025	private MyTimerTask mTimerTask;

026	int Y_axis[],//保存正弦波的Y轴上的点

027	centerY,//中心线

028	oldX,oldY,//上一个XY点

029	currentX;//当前绘制到的X轴上的点

030

031

@Override

032	public void onCreate(Bundle savedInstanceState) {

033	super.onCreate(savedInstanceState);

034	setContentView(R.layout.main);

035

036	btnSimpleDraw = (Button) this.findViewById(R.id.Button01);

037	btnTimerDraw = (Button) this.findViewById(R.id.Button02);

038	btnSimpleDraw.setOnClickListener(new ClickEvent());

039	btnTimerDraw.setOnClickListener(new ClickEvent());

040	sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01);

041	sfh = sfv.getHolder();

042

043	//动态绘制正弦波的定时器

044	mTimer = new Timer();

045	mTimerTask = new MyTimerTask();

046

047	// 初始化y轴数据

048	centerY = (getWindowManager().getDefaultDisplay().getHeight() - sfv

049	.getTop()) / 2;

050	Y_axis = new int[getWindowManager().getDefaultDisplay().getWidth()];

051	for (int i = 1; i < Y_axis.length; i++) {// 计算正弦波

052	Y_axis[i - 1] = centerY

053	- (int) (100 * Math.sin(i * 2 * Math.PI / 180));

054

}

055

}

056

057	class ClickEvent implements View.OnClickListener {

058

059

@Override

060	public void onClick(View v) {

061

062	if (v == btnSimpleDraw) {

063	SimpleDraw(Y_axis.length-1);//直接绘制正弦波

064

065	} else if (v == btnTimerDraw) {

066	oldY = centerY;

067	mTimer.schedule(mTimerTask, 0, 5);//动态绘制正弦波

068

}

069

070

}

071

072

}

073

074	class MyTimerTask extends TimerTask {

075

@Override

076	public void run() {

077

078	SimpleDraw(currentX);

079	currentX++;//往前进

080	if (currentX == Y_axis.length - 1) {//如果到了终点，则清屏重来

081	ClearDraw();

082	currentX = 0;

083	oldY = centerY;

084

}

085

}

086

087

}

088

089

/**

090

* 绘制指定区域

091

*/

092	void SimpleDraw(int length) {

093	if (length == 0)

094

oldX = 0;

095	Canvas canvas = sfh.lockCanvas(new Rect(oldX, 0, oldX + length,

096	getWindowManager().getDefaultDisplay().getHeight()));// 关键:获取画布

097	Log.i("Canvas:",

098	String.valueOf(oldX) + "," + String.valueOf(oldX + length));

099

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

}