CustomerScrollView.java

package com.cheng.animationstudy.customview.taobao;

import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.TranslateAnimation;
import android.widget.ScrollView;

/**
 *
 */
public class CustomerScrollView extends ScrollView {

    private View mView;
    private Rect mRect = new Rect();
    private float y;

    public CustomerScrollView(Context context) {
        super(context);
    }

    public CustomerScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public CustomerScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @SuppressLint("MissingSuperCall")
    @Override
    protected void onFinishInflate() {
        if (getChildCount() > 0) {
            this.mView = getChildAt(0);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if (mView == null) {
            return super.onTouchEvent(ev);
        } else {
            commOnTouchEvent(ev);
        }
        return super.onTouchEvent(ev);
    }

    private void commOnTouchEvent(MotionEvent ev) {
        int action = ev.getAction();
        switch (action) {
            case MotionEvent.ACTION_DOWN:
                y = ev.getY();
                break;
            case MotionEvent.ACTION_UP:
                if (isNeedAnimation()) {
                    animation();
                }
                break;
            case MotionEvent.ACTION_MOVE:
                final float preY = y;
                float nowY = ev.getY();
                int deltaY = (int) (preY - nowY);
                scrollBy(0, deltaY);
                y = nowY;
                if (isNeedMove()) {
                    if (mRect.isEmpty()) {
                        mRect.set(mView.getLeft(), mView.getTop(), mView.getRight(), mView.getBottom());
                    }
                    if(mView.getTop() - deltaY <1000 && mView.getTop() -deltaY > -1000){
                        mView.layout(mView.getLeft(), mView.getTop()-deltaY, mView.getRight(), mView.getBottom()-deltaY);
                    }
                }
                break;
        }
    }

    private boolean isNeedMove() {
        int offset = mView.getMeasuredHeight() - getHeight();
        int scrollY = getScrollY();
        if (scrollY==0 || scrollY==offset) {
            return true;
        }
        return false;
    }

    private boolean isNeedAnimation() {
        return !mRect.isEmpty();
    }

    private void animation() {
        TranslateAnimation ta = new TranslateAnimation(0, 0, mView.getTop(), mRect.top);
        ta.setDuration(200);
        mView.startAnimation(ta);
        mView.layout(mRect.left, mRect.top, mRect.right, mRect.bottom);
        mRect.setEmpty();
    }

}