第一步，先上工具类，通过监听根视图的高度变化来判断是否显示了软键盘

public class SoftKeyBoardListener {

    @SuppressLint("StaticFieldLeak")
    private Activity mActivity;
    private int rootViewVisibleHeight;      //纪录根视图的显示高度
    private OnSoftKeyBoardChangeListener onSoftKeyBoardChangeListener;
    private final View rootView;            //activity的根视图
    private final ViewTreeObserver viewTreeObserver;
    private final ViewTreeObserver.OnGlobalLayoutListener onGlobalLayoutListener;

    @SuppressLint("StaticFieldLeak")
    private volatile static SoftKeyBoardListener instance;

    public static SoftKeyBoardListener newInstance(Activity activity) {
        if (instance == null) {
            synchronized (SoftKeyBoardListener.class) {
                if (instance == null) {
                    instance = new SoftKeyBoardListener(activity);
                }
            }
        }
        return instance;
    }

    public void clearInstance(){
        mActivity = null;
        if(viewTreeObserver.isAlive()){
            viewTreeObserver.removeOnGlobalLayoutListener(onGlobalLayoutListener);
        }
        onSoftKeyBoardChangeListener = null;
        instance = null;
    }

    private SoftKeyBoardListener(Activity activity) {

        mActivity = activity;

        //获取activity的根视图
        rootView = mActivity.getWindow().getDecorView();

        viewTreeObserver = rootView.getViewTreeObserver();

        onGlobalLayoutListener = () -> {
            //获取当前根视图在屏幕上显示的大小
            Rect r = new Rect();
            rootView.getWindowVisibleDisplayFrame(r);

            int visibleHeight = r.height();
            System.out.println(""+visibleHeight);
            if (rootViewVisibleHeight == 0) {
                if (onSoftKeyBoardChangeListener != null) {
                    onSoftKeyBoardChangeListener.keyBoardShow(0);
                }
                rootViewVisibleHeight = visibleHeight;
                return;
            }

            //根视图显示高度没有变化，可以看作软键盘显示／隐藏状态没有改变
            if (rootViewVisibleHeight == visibleHeight) {
                return;
            }

            //根视图显示高度变小超过200，可以看作软键盘显示了
            if (rootViewVisibleHeight - visibleHeight > 200) {
                if (onSoftKeyBoardChangeListener != null) {
                    onSoftKeyBoardChangeListener.keyBoardShow(rootViewVisibleHeight - visibleHeight);
                }
                rootViewVisibleHeight = visibleHeight;
                return;
            }

            //根视图显示高度变大超过200，可以看作软键盘隐藏了
            if (visibleHeight - rootViewVisibleHeight > 200) {
                if (onSoftKeyBoardChangeListener != null) {
                    onSoftKeyBoardChangeListener.keyBoardHide(visibleHeight - rootViewVisibleHeight);
                }
                rootViewVisibleHeight = visibleHeight;
            }
        };

        viewTreeObserver.addOnGlobalLayoutListener(onGlobalLayoutListener);
    }

    public void setOnSoftKeyBoardChangeListener(OnSoftKeyBoardChangeListener onSoftKeyBoardChangeListener) {
        this.onSoftKeyBoardChangeListener = onSoftKeyBoardChangeListener;
    }

    public interface OnSoftKeyBoardChangeListener {
        void keyBoardShow(int height);
        void keyBoardHide(int height);
    }
}

第二步，调用

 /**
   * 监听软键盘的收起和弹出
   */
protected void backgroundLayoutListener() {
    SoftKeyBoardListener softKeyBoardListener = SoftKeyBoardListener.newInstance(activity);
    softKeyBoardListener.setOnSoftKeyBoardChangeListener(new SoftKeyBoardListener.OnSoftKeyBoardChangeListener() {
        @Override
        public void keyBoardShow(int height) {
            Log.d(TAG, "键盘显示 高度" + height);
        }

        @Override
        public void keyBoardHide(int height) {
            Log.d(TAG, "键盘隐藏 高度" + height);
            disMissDialogAndCacheInfo();
            softKeyBoardListener.clearInstance();
        }
    });
}