扩展SurfaceView的OnDraw（）方法从来没有所谓的

问题描述

我想修改我用做一个摄像头preVIEW，以显示覆盖广场SurfaceView。但是，扩展SurfaceView的OnDraw的方法不会被调用。

下面是源：

 公共类相机previewView延伸SurfaceView {

    保护面漆rectanglePaint =新的油漆（）;

    公共摄像头previewView（上下文的背景下，ATTRS的AttributeSet）{
        超（背景下，ATTRS）;
        rectanglePaint.setARGB（255，200，0，0）;
        rectanglePaint.setStyle（Paint.Style.FILL）;
        rectanglePaint.setStrokeWidth（2）;
    }

    @覆盖
    保护无效的OnDraw（帆布油画）{
        canvas.drawRect（新的矩形（10,10,200,200），rectanglePaint）;
        Log.w（this.getClass（）的getName（），关于抽奖之称。）;
    }
}

公共类相机preVIEW延伸活动实现SurfaceHolder.Callback {

    私人SurfaceHolder持有人;
    私人摄像头摄像头;

    @覆盖
    保护无效的onCreate（包savedInstanceState）{
        super.onCreate（savedInstanceState）;

        //我们删除了状态栏，标题栏，使应用程序全屏
        requestWindowFeature（Window.FEATURE_NO_TITLE）;
        getWindow（）。setFlags（WindowManager.LayoutParams.FLAG_FULLSCREEN，
                WindowManager.LayoutParams.FLAG_FULLSCREEN）;

        //我们设置的内容视图是我们做了布局
        的setContentView（R.layout.camera_ preVIEW）;

        //我们注册活动来处理SurfaceView的回调
        相机previewView surfaceView =（相机previewView）findViewById（R.id.camera_surface）;
        支架= surfaceView.getHolder（）;

        holder.addCallback（本）;
        holder.setType（SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS）;
    }

    公共无效surfaceChanged（SurfaceHolder持有人，INT格式，诠释的宽度，
            INT高度）{

        Camera.Parameters PARAMS = camera.getParameters（）;

        params.set previewSize（宽，高）;
        camera.setParameters（PARAMS）;

        尝试 {
            camera.set previewDisplay（保持器）;
        }赶上（IOException异常E）{
            e.printStackTrace（）;
        }

        camera.start preVIEW（）;

    }

    公共无效surfaceCreated（SurfaceHolder持有者）{
        相机= Camera.open（）;
    }

    公共无效surfaceDestroyed（SurfaceHolder持有者）{
        camera.stop preVIEW（）;
        camera.release（）;
    }


}
 

解决方案

发现它在Android的开发者谷歌组。您只需添加：

  setWillNotDraw（假）
 

要构造。现在，如果有人能解释我为什么，这将是极大的AP preciated。

I'm trying to modify the SurfaceView I use for doing a camera preview in order to display an overlaying square. However, the onDraw method of the extended SurfaceView is never called.

Here is the source :

public class CameraPreviewView extends SurfaceView {

    protected final Paint rectanglePaint = new Paint();

    public CameraPreviewView(Context context, AttributeSet attrs) {
        super(context, attrs);
        rectanglePaint.setARGB(255, 200, 0, 0);
        rectanglePaint.setStyle(Paint.Style.FILL);
        rectanglePaint.setStrokeWidth(2);
    }

    @Override
    protected void onDraw(Canvas canvas){
        canvas.drawRect(new Rect(10,10,200,200), rectanglePaint);
        Log.w(this.getClass().getName(), "On Draw Called");
    }
}

public class CameraPreview extends Activity implements SurfaceHolder.Callback{

    private SurfaceHolder holder;
    private Camera camera;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);

        // We remove the status bar, title bar and make the application fullscreen
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);

        // We set the content view to be the layout we made
        setContentView(R.layout.camera_preview);

        // We register the activity to handle the callbacks of the SurfaceView
        CameraPreviewView surfaceView = (CameraPreviewView) findViewById(R.id.camera_surface);
        holder = surfaceView.getHolder();

        holder.addCallback(this);
        holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }

    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {

        Camera.Parameters params = camera.getParameters();

        params.setPreviewSize(width, height);
        camera.setParameters(params);

        try {
            camera.setPreviewDisplay(holder);
        } catch (IOException e) {
            e.printStackTrace();
        }

        camera.startPreview();

    }

    public void surfaceCreated(SurfaceHolder holder) {
        camera = Camera.open();
    }

    public void surfaceDestroyed(SurfaceHolder holder) {
        camera.stopPreview();
        camera.release();   
    }


}

解决方案

Found it on the android-developers Google group. You simply have to add :

setWillNotDraw(false)

To the constructor. Now if someone could explain me why, that would be greatly appreciated.

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