RxKeyboardVisibilityDetector.java

public class RxKeyboardVisibilityDetector {
    public final static class Change {
        public final boolean visible;
        public final int height;
        Change(boolean visible, int height) {
            this.visible = visible;
            this.height = height;
        }
        @Override
        public String toString() {
            StringBuilder sb = new StringBuilder();
            sb.append("Keyboard.Visibility:").append(visible).append("\n");
            sb.append("Keyboard.Height:").append(height);
            return sb.toString();
        }
    }

    // Threshold for minimal keyboard height.
    final private static int MIN_KEYBOARD_HEIGHT_PX = 150;
    @NonNull
    public static Observable<Change> visibilityChanges(Activity activity) {
        return Observable.create(new Observable.OnSubscribe<Change>() {
            @Override
            public void call(Subscriber<? super Change> subscriber) {
                // Top-level window decor view.
                final View decorView = activity.getWindow().getDecorView();

                // Register global layout listener.
                decorView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
                    private final Rect windowVisibleDisplayFrame = new Rect();
                    private int lastVisibleDecorViewHeight;

                    @Override
                    public void onGlobalLayout() {
                        // Retrieve visible rectangle inside window.
                        decorView.getWindowVisibleDisplayFrame(windowVisibleDisplayFrame);
                        final int visibleDecorViewHeight = windowVisibleDisplayFrame.height();
                        Change change = null;
                        // Decide whether keyboard is visible from changing decor view height.
                        if (lastVisibleDecorViewHeight != 0) {
                            if (lastVisibleDecorViewHeight > visibleDecorViewHeight + MIN_KEYBOARD_HEIGHT_PX) {
                                // Calculate current keyboard height (this includes also navigation bar height when in fullscreen mode).
                                int currentKeyboardHeight = decorView.getHeight() - windowVisibleDisplayFrame.bottom;
                                // Notify listener about keyboard being shown.
                                change = new Change(true, currentKeyboardHeight);
                            } else if (lastVisibleDecorViewHeight + MIN_KEYBOARD_HEIGHT_PX < visibleDecorViewHeight) {
                                // Notify listener about keyboard being hidden.
                                change = new Change(false, 0);
                            }
                        }
                        // Save current decor view height for the next call.
                        lastVisibleDecorViewHeight = visibleDecorViewHeight;

                        if (!subscriber.isUnsubscribed()&&change!=null) {
                            subscriber.onNext(change);
                        }
                    }
                });
            }
        });

    }
}

用來判斷鍵盤是否出現，也擷取了高度。