21天學習android開發教程之SurfaceView

上一篇文章介紹了MediaPlayer相關內容，這次用兩篇文章來介紹SurfaceView的用法。網上介紹SurfaceView的用法有很多，寫法也層出不同，例如繼承SurfaceView類，或者繼承SurfaceHolder.Callback類等，這個可以根據功能實際需要自己選擇，我這裡就直接在普通的用戶界面調用SurfaceHolder的lockCanvas和unlockCanvasAndPost。
先來看看程序運行的截圖：

截圖1主要演示了直接把正弦波繪畫在SurfaceView上 

對比上面的左右兩圖，右圖用.lockCanvas(null)，而左圖用.lockCanvas(new Rect(oldX, 0, oldX + length,getWindowManager().getDefaultDisplay().getHeight()))，對比一下兩個效果，由於左圖是按指定Rect繪畫，所以效率會比右圖的全控件繪畫高些，並且在清屏之後(canvas.drawColor(Color.BLACK))不會留有上次繪畫的殘留。

接下來貼出main.xml的源碼:

<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="簡單繪畫">
        <button android:id="@+id/Button02" android:layout_width="wrap_content" 
            android:layout_height="wrap_content" android:text="定時器繪畫">
    
    <surfaceview android:id="@+id/SurfaceView01" 
        android:layout_width="fill_parent" android:layout_height="fill_parent">

接下來貼出程序源碼：

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軸上的點
    centerY,//中心線
    oldX,oldY,//上一個XY點 
    currentX;//當前繪制到的X軸上的點

    @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();

        //動態繪制正弦波的定時器
        mTimer = new Timer();
        mTimerTask = new MyTimerTask();

        // 初始化y軸數據
        centerY = (getWindowManager().getDefaultDisplay().getHeight() - sfv
                .getTop()) / 2;
        Y_axis = new int[getWindowManager().getDefaultDisplay().getWidth()];
        for (int i = 1; i < Y_axis.length; i++) {// 計算正弦波
            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);//直接繪制正弦波
            
            } else if (v == btnTimerDraw) {
                oldY = centerY;
                mTimer.schedule(mTimerTask, 0, 5);//動態繪制正弦波
            }

        }

    }

    class MyTimerTask extends TimerTask {
        @Override
        public void run() {

            SimpleDraw(currentX);
            currentX++;//往前進
            if (currentX == Y_axis.length - 1) {//如果到了終點，則清屏重來
                ClearDraw();
                currentX = 0;
                oldY = centerY;
            }
        }

    }
    
    /*
     * 繪制指定區域
     */
    void SimpleDraw(int length) {
        if (length == 0)
            oldX = 0;
        Canvas canvas = sfh.lockCanvas(new Rect(oldX, 0, oldX + length,
                getWindowManager().getDefaultDisplay().getHeight()));// 關鍵:獲取畫布
        Log.i("Canvas:",
                String.valueOf(oldX) + "," + String.valueOf(oldX + length));

        Paint mPaint = new Paint();
        mPaint.setColor(Color.GREEN);// 畫筆為綠色
        mPaint.setStrokeWidth(2);// 設置畫筆粗細

        int y;
        for (int i = oldX + 1; i < length; i++) {// 繪畫正弦波
            y = Y_axis[i - 1];
            canvas.drawLine(oldX, oldY, i, y, mPaint);
            oldX = i;
            oldY = y;
        }
        sfh.unlockCanvasAndPost(canvas);// 解鎖畫布，提交畫好的圖像
    }

    void ClearDraw() {
        Canvas canvas = sfh.lockCanvas(null);
        canvas.drawColor(Color.BLACK);// 清除畫布
        sfh.unlockCanvasAndPost(canvas);

    }
}

以上就是本文的全部內容，希望對大家學習Android軟件編程有所幫助。