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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。

程序运行的截图

imgs/asCode/08211521_SeCh.jpg

1.gif

imgs/asCode/08211643_C4Wz.gif

2.gif

imgs/asCode/08211643_zqsK.gif

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

    @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);

    }
}

标签:SurfaceView,Android,SDK

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