Error inflating when extending a class

user_451119 0
Viewed 131982

I'm trying to create a custom view GhostSurfaceCameraView that extends SurfaceView. Here's my class definition file

GhostSurfaceCameraView.java:

public class GhostSurfaceCameraView extends SurfaceView implements SurfaceHolder.Callback {
    SurfaceHolder mHolder;
    Camera mCamera;

    GhostSurfaceCameraView(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);
        parameters.set("orientation", "portrait");
        // parameters.setRotation(90); // API 5+
        mCamera.setParameters(parameters);
        mCamera.startPreview();
    }
}

And this is in my ghostviewscreen.xml:

<com.alpenglow.androcap.GhostSurfaceCameraView android:id="@+id/ghostview_cameraview"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"/>

Now in the activity I made: 

protected void onCreate(Bundle savedInstanceState) {
    try {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.ghostviewscreen);
    }
}

When setContentView() gets called, an exception is thrown: 

Binary XML file 09-17 22:47:01.958: ERROR/ERROR(337):
ERROR IN CODE:
android.view.InflateException: Binary
XML file line #14: Error inflating
class
com.alpenglow.androcap.GhostSurfaceCameraView

Can anyone tell me why I get this error? Thanks.

surfaceview class android xml java
10 Answers

In my case, I copied my class from somewhere else and didn't notice right away that it was an abstract class. You can't inflate abstract classes.

user_69024100

The thing to understand here is that:

The constructor ViewClassName(Context context, AttributeSet attrs ) is called when inflating the customView via xml. You see you are not using the new keyword to instantiate your object i.e. you are not doing new GhostSurfaceCameraView(). Doing this you are calling the first constructor i.e. public View (Context context).

Whereas when inflating view from XML, i.e. when using setContentView(R.layout.ghostviewscreen); or using findViewById, you, NO, not you!, the android system calls the ViewClassName(Context context, AttributeSet attrs ) constructor.

This is clear when reading the documentation : "Constructor that is called when inflating a view from XML." See: https://developer.android.com/reference/android/view/View.html#View(android.content.Context,%20android.util.AttributeSet)

Hence, never forget basic polymorphism and never forget reading through the documentation. It saves a ton of headache.

user_92467520
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