回到主題,SurfaceView和一般的View有什麼區別呢?SurfaceView不需要通過線程來更新視圖,但繪製之前通常必須使用SurfaceHolder(通過getHolder()方法獲取,是控制畫布大小和改變的對象)的lockCanvas方法鎖定(當SurfaceHolder的type設置爲SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS除外),然後用unclockCanvasAndPost釋放畫布。
SurfaceView畫布的變化和前面講的一樣,是通過SurfaceHoder來控制的,SurfaceHolder的addCallback方法註冊一個SurfaceView變化的跟蹤器,應用程序需要實現SurfaceHoder.Callback接口,這個接口有三個方法,分別是:
surfaceCreated: 在Surface被創建的時候觸發。
surfaceChanged:在Surface的大小改變的時候觸發。
surfaceDistoryed:在Surface被銷燬的時候觸發。
SurfaceHolder可以通過removeCallback來移除監聽。
package com.caravelsoft.surfaceview; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.util.AttributeSet; import android.view.SurfaceHolder; import android.view.SurfaceView; public class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback { private boolean mLoop = false; private SurfaceHolder mHolder = null; private int m_y = 50; private int mCount = 0; public MySurfaceView(Context context) { super(context); initView(); // TODO Auto-generated constructor stub } public MySurfaceView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); // TODO Auto-generated constructor stub initView(); } public MySurfaceView(Context context, AttributeSet attrs) { super(context, attrs); // TODO Auto-generated constructor stub initView(); } public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { // TODO Auto-generated method stub } public void surfaceCreated(SurfaceHolder holder) { // TODO Auto-generated method stub mLoop = true; new Thread(mRunner).start(); } public void surfaceDestroyed(SurfaceHolder holder) { // TODO Auto-generated method stub mLoop = false; } private void initView() { mHolder = this.getHolder(); mHolder.addCallback(this); this.setFocusable(true); } private Runnable mRunner = new Runnable() { public void run() { // TODO Auto-generated method stub while (mLoop) { try { Thread.sleep(200); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } synchronized (mHolder) { onDrawView(); } } } }; private void onDrawView() { if (mHolder == null) return; // 獲取畫布 Canvas canvas = mHolder.lockCanvas(); if (null == canvas) return; if (mCount < 100) { mCount++; } else { mCount = 0; } // 繪圖,定義畫筆 Paint paint = new Paint(); paint.setAntiAlias(true); paint.setColor(Color.BLACK); // 繪製矩形 canvas.drawRect(0, 0, 320, 480, paint); switch (mCount % 4) { case 0: paint.setColor(Color.BLUE); break; case 1: paint.setColor(Color.GREEN); break; case 2: paint.setColor(Color.LTGRAY); break; case 3: paint.setColor(Color.RED); break; } canvas.drawCircle((320 - 25) / 2, m_y, 50, paint); // 釋放canvas mHolder.unlockCanvasAndPost(canvas); } }