在实现一些IM页面，例如对话框，评论框时，常常会遇到键盘和表情panel显示/隐藏引起的闪屏问题。问题的根本原因是当键盘收起或弹出时，layout会发生变化，此时panel的高度的计算如果时机不对，那么会导致闪屏。

解决的办法有很多，这里提供一种重写onMeasure方法的实现：

使用方法：

    mEditText = (EditText) findViewById(R.id.editText);
    mPanel = (ViewGroup) findViewById(R.id.emotion_panel);

    mCommentPanelLayout = (CommentPanelLayout) findViewById(R.id.comment_panel_layout);
    mCommentPanelLayout.setListener(new CommentPanelLayout.SimpleListener() {
        @Override
        public void onKeyboardShow(View view) {
            Log.d(TAG, "onKeyboardShow() called");
        }

        @Override
        public void onKeyboardHide(View view) {
            Log.d(TAG, "onKeyboardHide() called");
        }

        @Override
        public void onPanelShow(View view) {
            Log.d(TAG, "onPanelShow() called");
        }

        @Override
        public void onPanelHide(View view) {
            Log.d(TAG, "onPanelHide() called");
        }
    });
    mCommentPanelLayout.setFocusTarget(mEditText); // 设定要监听的edittext
    mCommentPanelLayout.setPanelView(mPanel); // 设定panel对象

    findViewById(R.id.emotion_button).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (mCommentPanelLayout.isKeyboardShown()) {
                mCommentPanelLayout.switchToPanel();
            } else if (mCommentPanelLayout.isPanelShown()){
                mCommentPanelLayout.switchToKeyboard();
            } else if (!mCommentPanelLayout.isKeyboardShown() && !mCommentPanelLayout.isPanelShown()){
                mCommentPanelLayout.showPanel();
                // mCommentPanelLayout.showKeyboard(); // 当什么都没弹起的时候，点击按钮显示panel或者keyboard
            }
        }
    });

layout是这样的：

<your.package.CommentPanelLayout
    app:layout_constraintBottom_toBottomOf="parent"
    android:id="@+id/comment_panel_layout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@android:color/darker_gray">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <EditText
            android:id="@+id/editText"
            android:layout_width="match_parent"
            android:layout_height="42dp"
            android:gravity="center_vertical"
            android:layout_toLeftOf="@+id/emotion_button"
            android:hint="make a comment..."
            android:paddingLeft="10dp"
            android:paddingStart="10dp"/>

        <Button
            android:layout_alignParentEnd="true"
            android:id="@+id/emotion_button"
            android:text="emotion"
            android:layout_width="wrap_content"
            android:layout_height="42dp"/>
    </RelativeLayout>


    <RelativeLayout
        android:visibility="gone"
        android:id="@+id/emotion_panel"
        android:layout_width="match_parent"
        android:layout_height="150dp">

        <Button
            android:layout_centerInParent="true"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="This is a button"/>

    </RelativeLayout>

</your.package.CommentPanelLayout>

源码如下所示：