Attempt to invoke virtual method 'java.lang.Object java.lang.ref.WeakReference.get()' on a null object reference

[appsw]

In class CameraConnectionService code:
@OverRide
public void onCancel(final UsbDevice device) {
if (DEBUG) Log.d(TAG, "OnDeviceConnectListener#onCancel:");

            if (mWeakStateCallback.get() != null) {
                try {
                    mWeakStateCallback.get().onCancel(device);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

            synchronized (mConnectionSync) {
                mConnectionSync.notifyAll();
            }
        }

FATAL EXCEPTION: CameraConnection#258430995
Process: com.sample.liuyang, PID: 3166
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object java.lang.ref.WeakReference.get()' on a null object reference
at com.herohan.uvcapp.CameraConnectionService$CameraConnection$MyOnDeviceConnectListener.onCancel(CameraConnectionService.java:604)
at com.serenegiant.usb.USBMonitor.lambda$processCancel$2$com-serenegiant-usb-USBMonitor(USBMonitor.java:703)
at com.serenegiant.usb.USBMonitor$$ExternalSyntheticLambda1.run(D8$$SyntheticClass:0)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:223)
at android.os.HandlerThread.run(HandlerThread.java:67)

[shiyinghan]

The problem has been solved. Please pull the code and try again

[milosfec]

Each call to mWeakStateCallback.get() can return null, so the code if (mWeakStateCallback.get() != null) mWeakStateCallback.get().doSomething(); can throw null pointer exception, as garbage collector can release it anytime between any two instructions. You have to keep local reference to the object to prevent garbage collection while you are using the object.

if (mWeakStateCallback != null) {
    ICameraHelper.StateCallback callback = mWeakStateCallback.get()
    if (callback != null) {
        callback.doSomething()
    }
}

[shiyinghan]

Each call to mWeakStateCallback.get() can return null, so the code if (mWeakStateCallback.get() != null) mWeakStateCallback.get().doSomething(); can throw null pointer exception, as garbage collector can release it anytime between any two instructions. You have to keep local reference to the object to prevent garbage collection while you are using the object.

if (mWeakStateCallback != null) {
    ICameraHelper.StateCallback callback = mWeakStateCallback.get()
    if (callback != null) {
        callback.doSomething()
    }
}

Thanks. Fixed in new commit (506192e).