Android监听键盘状态变化

如下监听键盘状态变化的代码摘自React native的键盘状态监听代码，

这个方法会影响部分性能，正常情况下可以忽略。

import android.graphics.Rect;import android.support.annotation.Nullable;import android.util.DisplayMetrics;import android.view.View;import android.view.ViewTreeObserver;/** * Keyboard status monitor. * * usage： * * View view;//View must be had added to the View Tree * * * view.getViewTreeObserver().addOnGlobalLayoutListener(new KeyboardListener(view){ * *     @Override *     public void keyboardStatusChanged(boolean keyboardDidShow, @Nullable KeyboardInfo params){ *          if(keyboardDidShow){ *              //showing or height changed *          }else{ *              //hidden *          } *     } * * }); */public abstract class KeyboardListener implements ViewTreeObserver.OnGlobalLayoutListener {    private int mKeyboardHeight = 0;    private final Rect mVisibleViewArea = new Rect();    private View view;    private DisplayMetrics mDisplayMetrics;    public KeyboardListener(View view) {        if (view == null) {            throw new NullPointerException("view is null");        }        mDisplayMetrics = view.getContext().getResources().getDisplayMetrics();        this.view = view;    }    @Override    public void onGlobalLayout() {        View rootView = view.getRootView();        if (rootView == null) {            return;        }        rootView.getWindowVisibleDisplayFrame(mVisibleViewArea);        final int heightDiff =                mDisplayMetrics.heightPixels - mVisibleViewArea.bottom;        if (mKeyboardHeight != heightDiff && heightDiff > 0) {            // keyboard is now showing, or the keyboard height has changed            mKeyboardHeight = heightDiff;            KeyboardInfo keyboardInfo = new KeyboardInfo();            keyboardInfo.screenX = mVisibleViewArea.left;            keyboardInfo.screenY = mVisibleViewArea.bottom;            keyboardInfo.width = mVisibleViewArea.width();            keyboardInfo.height = mKeyboardHeight;            sendEvent(true, keyboardInfo);        } else if (mKeyboardHeight != 0 && heightDiff == 0) {            // keyboard is now hidden            mKeyboardHeight = heightDiff;            sendEvent(false, null);        }    }    private void sendEvent(boolean keyboardDidShow, @Nullable KeyboardInfo keyboardInfo) {        keyboardStatusChanged(keyboardDidShow, keyboardInfo);    }    public abstract void keyboardStatusChanged(boolean keyboardDidShow, @Nullable KeyboardInfo params);    public static class KeyboardInfo {        /**         * screen x pixle         */        public double screenY;        public double screenX;        public double width;        public double height;    }}