Question

我是上下文android的初学者。我已经写了一个android项目，它使用opencv从前置摄像头捕获帧，最后只需借助2个按钮转换灰度或rbga帧。想到的是，当点击按钮“GrayScale”时，图像将以灰度等转换为rgba，但是当我在项目中添加按钮时，我的应用程序就会崩溃。

java文件，基本方法：

//variables
protected static final String TAG = null;
private Camera camera;
private CameraBridgeViewBase mOpenCvCameraView;
private CvCameraViewFrame inputFrame;
private int CameraMod,GrayScale=0,RGBA=0;
private Button button1,button2;
private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this)
{
    @Override
    public void onManagerConnected(int status)
    {
        switch (status)
        {
            case LoaderCallbackInterface.SUCCESS:
            {
                Log.i(TAG,"OpenCV loaded successfully");
                mOpenCvCameraView.enableView();
                break;
            }
            default:
            {
                super.onManagerConnected(status);
                break;
            }
        }
    }
};
@Override
protected void onCreate(Bundle savedInstanceState) 
{
    Log.i(TAG,"called onCreate");
    super.onCreate(savedInstanceState);
    getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
    button1 = (Button) findViewById(R.id.GrayScale);
    button2 = (Button) findViewById(R.id.RGBA);
    button1.setOnClickListener(new View.OnClickListener() 
    {
        @Override
        public void onClick(View v) 
        {
            // TODO Auto-generated method stub
            GrayScale=1;
            RGBA=0;
        };
    });
    button2.setOnClickListener(new View.OnClickListener() 
    {   
        @Override
        public void onClick(View v) 
        {
            // TODO Auto-generated method stub
            RGBA=1;
            GrayScale=0;
        };
    });
    setContentView(R.layout.activity_main);
    mOpenCvCameraView = (CameraBridgeViewBase) findViewById(R.id.HelloOpenCvView);
    mOpenCvCameraView.setVisibility(SurfaceView.VISIBLE);
    CameraMod=camera.getNumberOfCameras();
    if (CameraMod >= 2)
    {
        mOpenCvCameraView.setCameraIndex(CameraBridgeViewBase.CAMERA_ID_FRONT);
    }
    else 
    {
        mOpenCvCameraView.setCameraIndex(CameraBridgeViewBase.CAMERA_ID_BACK);
    }
    mOpenCvCameraView.setCvCameraViewListener(this);
}
@Override
public Mat onCameraFrame(CvCameraViewFrame inputFrame) 
{
    Mat image = null;
    if (GrayScale==1)
    {
        image = inputFrame.gray();
    }
    if (RGBA==1)
    {
        image = inputFrame.rgba();
    }
    if (CameraMod >= 2)
    {
        Core.flip(image, image, 1);
    }


    return image;
};

xml文件包含按钮：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:opencv="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<Button 
    android:text="GrayScale"
    android:id="@+id/GrayScale"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>      
<Button 
    android:text="RGBA"
    android:id="@+id/RGBA"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>

<org.opencv.android.JavaCameraView
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:visibility="gone"
    android:id="@+id/HelloOpenCvView"
    opencv:show_fps="true"
    opencv:camera_id="any" />

Answer 1

您在通过setContentView()查看您的观看次数后致电findViewById()，这是错误的。您的视图（即按钮）必须为null。在通过setContentView()查找视图之前，请务必致电findViewById()。

@Override
protected void onCreate(Bundle savedInstanceState) 
{
    Log.i(TAG,"called onCreate");
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
    // Other code
}

添加按钮时android opencv崩溃

1 个答案: