Hello, I like where this is going. I hope these suggestions help you building a robust tool people can use:

1)

Ditch ìnitWith as it does nothing. Have a public KeyboardWatcher(Activity activity) constructor instead. The client activity will hold a reference to an instance. So you can have multiple activities using keyboard watcher at the same time. Activity will create an instance in onCreate and keep it.

2)

Use a more robust way to get the root view. android.R.id.content can change by calling Activity.setContentView(...). Activity.getWindow().getDecorView().getRootView() will not. See http://stackoverflow.com/a/11553582/2444099. Store the reference right after you get the activity in constructor.

3)

Define private final ViewTreeObserver.OnGlobalLayoutListener viewTreeObserverListener = new GlobalLayoutListener(); You can do this because rootView is resolved at the point of execution.

4)

Use weak references for activity, rootView and onKeyboardToggleListener. As soon as the activity is destroyed, you lose the references and prevent leaks.

5)

Rename bindKeyboardWatcher to setListener. Remove unbindKeyboardWatcher because setListener(null).

6)

Consider having addListener and removeListener instead of setListener.

This problem happen when activity attribut: android:configChanges="orientation" is used in the manifest. With this attribute set, the activity is not destroyed/recreated when we change orientation. That mean that KeyboardWatcher is not destroyed/recreated neither. So the initialValue is now wrong and since the detection of the presence of the keyboard is base on that, onKeyboardClosed() and onKeyboardShown() are thrown wrongly. So it would be nice to add support for that use case, for example add a resetInitialValue method or something like that.

For now the solution I found is to destroy/recreate the KeyboardWatcher in the onConfigurationChanged method:

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);

    if (mKeyboardWatcher != null) {
        mKeyboardWatcher.destroy();
        mKeyboardWatcher = new KeyboardWatcher(this);
        mKeyboardWatcher.setListener(this);
    }
}

when ths theam of activity like this "android:theme="@android:style/Theme.Holo.Light.NoActionBar.Fullscreen"，it is not work，i feel that "AndroidBug5497Workaround" will be helpful for this problem，but i failed !

I have found issue in keyboard height calculation after device rotate. The solution is to calculate keyboard height initialValue - rootViewRef.get().getHeight() in KeyboardWatcher.GlobalLayoutListener:onGlobalLayout() after keyboard has already finished slide from bottom animation. I need hotfix for my project right now so I used new Handler().postDelayed(() -> {//onGlobalLayout method content//}, 1000); but there should be better solution

if (initialValue == 0) { initialValue = rootViewRef.get().getHeight(); } else { if (initialValue > rootViewRef.get().getHeight()) { if (onKeyboardToggleListenerRef.get() != null) { if (!hasSentInitialAction || !isKeyboardShown) { isKeyboardShown = true; onKeyboardToggleListenerRef.get().onKeyboardShown(initialValue - rootViewRef.get().getHeight()); } } } else { if (!hasSentInitialAction || isKeyboardShown) { isKeyboardShown = false; rootViewRef.get().post(new Runnable() { @Override public void run() { if (onKeyboardToggleListenerRef.get() != null) { onKeyboardToggleListenerRef.get().onKeyboardClosed(); } } }); } } hasSentInitialAction = true; }