Realization effect

No picture say a xx, let's take a look at the renderings first!

Effect realization

Combined with the renderings, we have a careful analysis. In fact, it is not so difficult to implement. The main logic is to control the pop-up and display of the bottom view.
1. First, we customize a ViewGroup and measure all child view s

 public EmojiKeyBoardLayout(Context context) {
        this(context,null);
    }

    public EmojiKeyBoardLayout(Context context, AttributeSet attrs) {
        this(context, attrs,0);
    }

    public EmojiKeyBoardLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mScroller = new Scroller(context);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        measureChildren(widthMeasureSpec,heightMeasureSpec);
    }

2. The initial position of the bottom View is at the bottom of the screen. We layout the child views in onLayout.

 @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {
        for (int i = 0; i <getChildCount(); i++) {
            View child = getChildAt(i);
            if (i==0){
                contentView =child;
                //First childview, full screen
                child.layout(0,0,child.getMeasuredWidth(),child.getMeasuredHeight());
            }else{
                bottomView =child;
                child.layout(0,contentView.getMeasuredHeight(),child.getMeasuredWidth(),contentView.getMeasuredHeight()+child.getMeasuredHeight());
            }
        }
    }

3. The rest is the bottom View pop-up and display operation. We use the Scroller to achieve elastic sliding.

 public void showBottomView(){
        if (getScrollY()==0){
            hideKeyBoard();
            mScroller.startScroll(0,0,0,bottomView.getMeasuredHeight());
            invalidate();
        }
    }

    public void closeBottomView(){
        hideKeyBoard();
        mScroller.startScroll(0,getScrollY(),0,-getScrollY());
        invalidate();
    }

    @Override
    public void computeScroll() {
        if (mScroller.computeScrollOffset()){
            scrollTo(mScroller.getCurrX(),mScroller.getCurrY());
            postInvalidate();
        }
    }

There are so many core codes, which are basically routine operations. Reading thousands of books is better than walking thousands of miles. No matter how much code you read, if you don't practice, it will always be someone else's code.