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>
