SurfaceView繪圖機制

雖然前面都使用的View來進行繪圖，但View繪圖機制存在兩個缺陷：

1、缺乏雙緩衝機制

2、更新映像時，必須更新View上的整張圖片，效率低。

所以在遊戲繪製中推薦使用SurfaceView。它可以只對指定地區進行更新，可以提高效率。下面用一個簡單樣本來示範SurfaceView的使用：

Activity：

package com.home.activity;import android.app.Activity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Rect;import android.os.Bundle;import android.view.MotionEvent;import android.view.SurfaceHolder;import android.view.SurfaceHolder.Callback;import android.view.SurfaceView;import android.view.View;import android.view.View.OnTouchListener;import com.home.surfaceviewtest.R;public class SurfaceViewActivity extends Activity {// SurfaceHolder負責維護SurfaceView上繪製的內容private SurfaceHolder holder;private Paint paint;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);paint = new Paint();// 擷取SurfaceView執行個體SurfaceView surface = (SurfaceView) findViewById(R.id.main_sv);// 初始化SurfaceHolder對象holder = surface.getHolder();holder.addCallback(new Callback() {//當surface將要被銷毀時回調該方法@Overridepublic void surfaceDestroyed(SurfaceHolder holder) {}//當surface被建立時回調該方法@Overridepublic void surfaceCreated(SurfaceHolder holder) {// 鎖定整個SurfaceViewCanvas canvas = holder.lockCanvas();// 擷取背景資源Bitmap bitmap = BitmapFactory.decodeResource(SurfaceViewActivity.this.getResources(),R.drawable.image2);// 繪製背景canvas.drawBitmap(bitmap, 0, 0, null);// 繪製完成，釋放畫布，提交修改holder.unlockCanvasAndPost(canvas);// 重新鎖兩次，避免下次lockCanvas遮擋holder.lockCanvas(new Rect(0, 0, 0, 0));holder.unlockCanvasAndPost(canvas);holder.lockCanvas(new Rect(0, 0, 0, 0));holder.unlockCanvasAndPost(canvas);}//當一個surface的格式或大小發生改變時回調該方法@Overridepublic void surfaceChanged(SurfaceHolder holder, int format,int width, int height) {}});surface.setOnTouchListener(new OnTouchListener() {@Overridepublic boolean onTouch(View v, MotionEvent event) {// 只處理按下事件if (event.getAction() == MotionEvent.ACTION_DOWN) {int cx = (int) event.getX();int cy = (int) event.getY();// 鎖定SurfaceView的局部地區，只更新局部內容Canvas canvas = holder.lockCanvas(new Rect(cx - 60,cy - 60, cx + 60, cy + 60));// 儲存canvas的目前狀態canvas.save();// 旋轉畫布canvas.rotate(30, cx, cy);paint.setColor(Color.RED);// 繪製紅色方塊canvas.drawRect(cx - 40, cy - 40, cx, cy, paint);// 恢複canvas之前的儲存狀態canvas.restore();paint.setColor(Color.GREEN);// 繪製綠色方塊canvas.drawRect(cx, cy, cx + 40, cy + 40, paint);// 繪製完成，釋放畫布，提交修改holder.unlockCanvasAndPost(canvas);}return false;}});}}

 

布局XML：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <SurfaceView        android:id="@+id/main_sv"        android:layout_width="match_parent"        android:layout_height="match_parent"/></LinearLayout>