android画图-----图像预览

真高不明白 图像预览的例子 竟然放在这里，我觉得放在照相机那里边更好一些，这个例子很简单，就是先要获得图像预览的持有者 SurfaceHolder，然后相机通过它得到一个浏览的窗口。但是最主要 也是为啥把这个例子放在这 就是因为SurfaceHolder必须添加一个监听器实现几个接口：
class Preview extends SurfaceView implements SurfaceHolder.Callback {
    SurfaceHolder mHolder;
    Camera mCamera;
   
    Preview(Context context) {
        super(context);
       
        // Install a SurfaceHolder.Callback so we get notified when the
        // underlying surface is created and destroyed.
        mHolder = getHolder();
        mHolder.addCallback(this);
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceCreated(SurfaceHolder holder) {
        // The Surface has been created, acquire the camera and tell it where
        // to draw.
        mCamera = Camera.open();
        try {
           mCamera.setPreviewDisplay(holder);
        } catch (IOException exception) {
            mCamera.release();
            mCamera = null;
            // TODO: add more exception handling logic here
        }
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        // Surface will be destroyed when we return, so stop the preview.
        // Because the CameraDevice object is not a shared resource, it's very
        // important to release it when the activity is paused.
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
        // Now that the size is known, set up the camera parameters and begin
        // the preview.
        Camera.Parameters parameters = mCamera.getParameters();
        parameters.setPreviewSize(w, h);
        mCamera.setParameters(parameters);
        mCamera.startPreview();
    }

}

public class CameraPreview extends Activity {   
    private Preview mPreview;
   
    @Override
protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
       
        // Hide the window title.
        requestWindowFeature(Window.FEATURE_NO_TITLE);
   
        // Create our Preview view and set it as the content of our activity.
        mPreview = new Preview(this);
        setContentView(mPreview);
    }

}

这里面用到最多的就是相机的设置了不说了。