Android SurfaceView 的應用

文章目錄

• main.xml

SurfaceView 由於可以直接從記憶體或者DMA等硬體介面取得映像資料，因此是個非常重要的繪圖容器，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使用者介面調用SurfaceHolder的lockCanvas和 unlockCanvasAndPost。

對比下面的第二、三兩圖，三圖用.lockCanvas(null)，而二圖用.lockCanvas(new Rect(oldX, 0, oldX + length, getWindowManager().getDefaultDisplay().getHeight()))，對比一下兩個效果，由於二圖是按指定Rect繪畫，所以效率會比三圖的全控制項繪畫高些，並且在清屏之後 (canvas.drawColor(Color.BLACK))不會留有上次繪畫的殘留。

 

 

 

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="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>

　　

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[],//儲存正弦波的Y軸上的點centerY,//中心線oldX,oldY,//上一個XY點 currentX;//當前繪製到的X軸上的點@Overridepublic 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();//動態繪製正弦波的定時器mTimer = new Timer();mTimerTask = new MyTimerTask();// 初始化y軸資料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 {@Overridepublic void onClick(View v) {if (v == btnSimpleDraw) {SimpleDraw(Y_axis.length-1);//直接繪製正弦波} else if (v == btnTimerDraw) {oldY = centerY;mTimer.schedule(mTimerTask, 0, 5);//動態繪製正弦波}}}class MyTimerTask extends TimerTask {@Overridepublic 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;}}}/** * 繪製指定地區 */void SimpleDraw(int length) {if (length == 0)oldX = 0;Canvas canvas = sfh.lockCanvas(new Rect(oldX, 0, oldX + length,getWindowManager().getDefaultDisplay().getHeight()));// 關鍵:擷取畫布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);// 設定畫筆粗細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，提交畫好的映像}void ClearDraw() {Canvas canvas = sfh.lockCanvas(null);canvas.drawColor(Color.BLACK);// 清除畫布sfh.unlockCanvasAndPost(canvas);}}

　　

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