21天学习android开发教程之SurfaceView

Elaine ·

更新时间:2024-11-11

· 634 次阅读

上一篇文章介绍了MediaPlayer相关内容，这次用两篇文章来介绍SurfaceView的用法。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。
先来看看程序运行的截图：

截图1主要演示了直接把正弦波绘画在SurfaceView上

对比上面的左右两图，右图用.lockCanvas(null)，而左图用.lockCanvas(new Rect(oldX, 0, oldX + length,getWindowManager().getDefaultDisplay().getHeight()))，对比一下两个效果，由于左图是按指定Rect绘画，所以效率会比右图的全控件绘画高些，并且在清屏之后(canvas.drawColor(Color.BLACK))不会留有上次绘画的残留。

接下来贴出main.xml的源码:


<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 android:id="@+id/Button02" android:layout_width="wrap_content" 
            android:layout_height="wrap_content" android:text="定时器绘画">
    <surfaceview android:id="@+id/SurfaceView01" 
        android:layout_width="fill_parent" android:layout_height="fill_parent">

接下来贴出程序源码：


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) {//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);
    }
}

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