前文介紹了Android中MediaPlayer用法的時候稍微介紹了SurfaceView，SurfaceView由于可以直接從內存或者DMA等硬件接口取得圖像數據，因此是個非常重要的繪圖容器，這次我就來較為詳細的介紹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，本文所述方法就直接在普通的用戶界面調用SurfaceHolder的lockCanvas和unlockCanvasAndPost。
先來看看程序運行效果的截圖如下：
截圖1主要演示了直接把正弦波繪畫在SurfaceView上。
再來看看下面兩幅截圖：
對比上面的上下兩圖，下圖用.lockCanvas(null)，而上圖用.lockCanvas(new Rect(oldX, 0, oldX + length,
getWindowManager().getDefaultDisplay().getHeight()))，對比一下兩個效果，由于上圖是按指定Rect繪畫，所以效率會比下圖的全控件繪畫高些，并且在清屏之后(canvas.drawColor(Color.BLACK))不會留有上次繪畫的殘留。
main.xml的源碼如下:
<?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="簡單繪畫"></Button> <Button android:id="@+id/Button02" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="定時器繪畫"></Button> </LinearLayout> <SurfaceView android:id="@+id/SurfaceView01" android:layout_width="fill_parent" android:layout_height="fill_parent"></SurfaceView></LinearLayout>
接下來貼出Java程序源碼如下：
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); }}這里還需要注意一下： for (int i = oldX + 1; i < length; i++) {// 繪畫正弦波 這句，在.lockCanvas()指定Rect內減少循環畫線的次數，可以提高繪圖效率。
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