SurfaceView绘图机制
虽然前面都使用的View来进行绘图，但View绘图机制存在两个缺陷：
1、缺乏双缓冲机制
2、更新图像时，必须更新View上的整张图片，效率低。
所以在游戏绘制中推荐使用SurfaceView。它可以只对指定区域进行更新，可以提高效率。下面用一个简单示例来演示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负责维护SurfaceView上绘制的内容 private SurfaceHolder holder; private Paint paint; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); paint = new Paint(); // 获取SurfaceView实例 SurfaceView surface = (SurfaceView) findViewById(R.id.main_sv); // 初始化SurfaceHolder对象 holder = surface.getHolder(); holder.addCallback(new Callback() { //当surface将要被销毁时回调该方法 @Override public void surfaceDestroyed(SurfaceHolder holder) { } //当surface被创建时回调该方法 @Override public void surfaceCreated(SurfaceHolder holder) { // 锁定整个SurfaceView Canvas canvas = holder.lockCanvas(); // 获取背景资源 Bitmap bitmap = BitmapFactory.decodeResource( SurfaceViewActivity.this.getResources(), R.drawable.image2); // 绘制背景 canvas.drawBitmap(bitmap, 0, 0, null); // 绘制完成，释放画布，提交修改 holder.unlockCanvasAndPost(canvas); // 重新锁两次，避免下次lockCanvas遮挡 holder.lockCanvas(new Rect(0, 0, 0, 0)); holder.unlockCanvasAndPost(canvas); holder.lockCanvas(new Rect(0, 0, 0, 0)); holder.unlockCanvasAndPost(canvas); } //当一个surface的格式或大小发生改变时回调该方法 @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { } }); surface.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { // 只处理按下事件 if (event.getAction() == MotionEvent.ACTION_DOWN) { int cx = (int) event.getX(); int cy = (int) event.getY(); // 锁定SurfaceView的局部区域，只更新局部内容 Canvas canvas = holder.lockCanvas(new Rect(cx - 60, cy - 60, cx + 60, cy + 60)); // 保存canvas的当前状态 canvas.save(); // 旋转画布 canvas.rotate(30, cx, cy); paint.setColor(Color.RED); // 绘制红色方块 canvas.drawRect(cx - 40, cy - 40, cx, cy, paint); // 恢复canvas之前的保存状态 canvas.restore(); paint.setColor(Color.GREEN); // 绘制绿色方块 canvas.drawRect(cx, cy, cx + 40, cy + 40, paint); // 绘制完成，释放画布，提交修改 holder.unlockCanvasAndPost(canvas); } return false; } }); } } 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负责维护SurfaceView上绘制的内容 private SurfaceHolder holder; private Paint paint; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); paint = new Paint(); // 获取SurfaceView实例 SurfaceView surface = (SurfaceView) findViewById(R.id.main_sv); // 初始化SurfaceHolder对象 holder = surface.getHolder(); holder.addCallback(new Callback() { //当surface将要被销毁时回调该方法 @Override public void surfaceDestroyed(SurfaceHolder holder) { } //当surface被创建时回调该方法 @Override public void surfaceCreated(SurfaceHolder holder) { // 锁定整个SurfaceView Canvas canvas = holder.lockCanvas(); // 获取背景资源 Bitmap bitmap = BitmapFactory.decodeResource( SurfaceViewActivity.this.getResources(), R.drawable.image2); // 绘制背景 canvas.drawBitmap(bitmap, 0, 0, null); // 绘制完成，释放画布，提交修改 holder.unlockCanvasAndPost(canvas); // 重新锁两次，避免下次lockCanvas遮挡 holder.lockCanvas(new Rect(0, 0, 0, 0)); holder.unlockCanvasAndPost(canvas); holder.lockCanvas(new Rect(0, 0, 0, 0)); holder.unlockCanvasAndPost(canvas); } //当一个surface的格式或大小发生改变时回调该方法 @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { } }); surface.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { // 只处理按下事件 if (event.getAction() == MotionEvent.ACTION_DOWN) { int cx = (int) event.getX(); int cy = (int) event.getY(); // 锁定SurfaceView的局部区域，只更新局部内容 Canvas canvas = holder.lockCanvas(new Rect(cx - 60, cy - 60, cx + 60, cy + 60)); // 保存canvas的当前状态 canvas.save(); // 旋转画布 canvas.rotate(30, cx, cy); paint.setColor(Color.RED); // 绘制红色方块 canvas.drawRect(cx - 40, cy - 40, cx, cy, paint); // 恢复canvas之前的保存状态 canvas.restore(); paint.setColor(Color.GREEN); // 绘制绿色方块 canvas.drawRect(cx, cy, cx + 40, cy + 40, paint); // 绘制完成，释放画布，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> <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>
