Android SurfaceView

今天介绍一下SurfaceView的用法，SurfaceView一般与SurfaceHolder结合使用，SurfaceHolder用于向与之关联的SurfaceView上绘图，调用SurfaceView的getHolder()方法即可获取SurfaceView关联的SurfaceHolder。

SurfaceHolder提供一下几个方法来获取Canvas对象：

Canvas lockCanvas()：锁定整个SurfaceView对象，获取该Surface上的Canvas。

Canvas lockCanvas(Rect dirty)：锁定SurfaceView上Rect划分的区域，获取该Surface上的Canvas。

当通过lockCanvas获取指定SurfaceView上的Canvas之后，接下来程序就可以调用Canvas进行绘图，绘图完成后，调用一下方法来释放绘图、提交所绘制的图形：

unlockCanvasAndPost(canvas)。

下面直接上个实例：

 public class SurfaceViewTest extends Activity

 {

     // SurfaceHolder负责维护SurfaceView上绘制的内容

     private SurfaceHolder holder;

     private Paint paint;

     @Override

     public void onCreate(Bundle savedInstanceState)

     {

         super.onCreate(savedInstanceState);

         setContentView(R.layout.main);

         paint = new Paint();

         SurfaceView surface = (SurfaceView) findViewById(R.id.show);

         // 初始化SurfaceHolder对象

         holder = surface.getHolder();

         holder.addCallback(new Callback()

         {

             @Override

             public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2,

                 int arg3)

             {

             }

             @Override

             public void surfaceCreated(SurfaceHolder holder)

             {

                 // 锁定整个SurfaceView

                 Canvas canvas = holder.lockCanvas();

                 // 绘制背景

                 Bitmap back = BitmapFactory.decodeResource(

                     SurfaceViewTest.this.getResources(), R.drawable.sun);

                 //绘制背景

                 canvas.drawBitmap(back, 0, 0, null);

                 // 绘制完成，释放画布，提交修改

                 holder.unlockCanvasAndPost(canvas);

                 //重新锁一次，"持久化"上次所绘制的内容

                 holder.lockCanvas(new Rect(0, 0, 0, 0));

                 holder.unlockCanvasAndPost(canvas);

             }

             @Override

             public void surfaceDestroyed(SurfaceHolder holder)

             {

             }

         });

         //为surface的触摸事件绑定监听器

         surface.setOnTouchListener(new OnTouchListener()

         {

             @Override

             public boolean onTouch(View source, 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 - 50,

                         cy - 50, cx + 50, cy + 50));

                     // 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;

             }

         });

     }

 }

巴特西

Android SurfaceView

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