绘图 surfaceView 2

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

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。

标签： SurfaceView Android SDK

代码片段(5)

[图片] 程序运行的截图

[图片] 1.gif

[图片] 2.gif

[代码] main.xml

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<?xml version="1.0" encoding="utf-8"?>

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<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

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

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    android:orientation="vertical">

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    <LinearLayout android:id="@+id/LinearLayout01"

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

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        <Button android:id="@+id/Button01" android:layout_width="wrap_content"

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            android:layout_height="wrap_content" android:text="简单绘画"></Button>

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        <Button android:id="@+id/Button02" android:layout_width="wrap_content"

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            android:layout_height="wrap_content" android:text="定时器绘画"></Button>

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    </LinearLayout>

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    <SurfaceView android:id="@+id/SurfaceView01"

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        android:layout_width="fill_parent" android:layout_height="fill_parent"></SurfaceView>

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</LinearLayout>

[代码] TestSurfaceView.java

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package com.testSurfaceView;

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import java.util.Timer;

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import java.util.TimerTask;

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import android.app.Activity;

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import android.graphics.Canvas;

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import android.graphics.Color;

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import android.graphics.Paint;

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import android.graphics.Rect;

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import android.os.Bundle;

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import android.util.Log;

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import android.view.SurfaceHolder;

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import android.view.SurfaceView;

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import android.view.View;

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import android.widget.Button;

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public class TestSurfaceView extends Activity {

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

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    Button btnSimpleDraw, btnTimerDraw;

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    SurfaceView sfv;

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    SurfaceHolder sfh;

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    private Timer mTimer;

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    private MyTimerTask mTimerTask;

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    int Y_axis[],//保存正弦波的Y轴上的点

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    centerY,//中心线

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    oldX,oldY,//上一个XY点

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    currentX;//当前绘制到的X轴上的点

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    @Override

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    public void onCreate(Bundle savedInstanceState) {

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        super.onCreate(savedInstanceState);

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        setContentView(R.layout.main);

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

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

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        btnSimpleDraw.setOnClickListener(new ClickEvent());

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        btnTimerDraw.setOnClickListener(new ClickEvent());

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

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        sfh = sfv.getHolder();

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        //动态绘制正弦波的定时器

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        mTimer = new Timer();

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        mTimerTask = new MyTimerTask();

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        // 初始化y轴数据

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

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                .getTop()) / 2;

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

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

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            Y_axis[i - 1] = centerY

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

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        }

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    }

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    class ClickEvent implements View.OnClickListener {

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        @Override

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        public void onClick(View v) {

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            if (v == btnSimpleDraw) {

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

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            } else if (v == btnTimerDraw) {

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                oldY = centerY;

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

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            }

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        }

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    }

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    class MyTimerTask extends TimerTask {

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        @Override

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        public void run() {

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            SimpleDraw(currentX);

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            currentX++;//往前进

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

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                ClearDraw();

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                currentX = 0;

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                oldY = centerY;

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            }

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        }

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    }

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    /**

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     * 绘制指定区域

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     */

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    void SimpleDraw(int length) {

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        if (length == 0)

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            oldX = 0;

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

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

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        Log.i("Canvas:",

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

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        Paint mPaint = new Paint();

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        mPaint.setColor(Color.GREEN);// 画笔为绿色

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        mPaint.setStrokeWidth(2);// 设置画笔粗细

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        int y;

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        for (int i = oldX + 1; i < length; i++) {// 绘画正弦波

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            y = Y_axis[i - 1];

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            canvas.drawLine(oldX, oldY, i, y, mPaint);

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            oldX = i;

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            oldY = y;

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        }

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        sfh.unlockCanvasAndPost(canvas);// 解锁画布，提交画好的图像

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    }

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    void ClearDraw() {

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        Canvas canvas = sfh.lockCanvas(null);

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        canvas.drawColor(Color.BLACK);// 清除画布

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        sfh.unlockCanvasAndPost(canvas);

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    }

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}