BorderScrollView.java

/*
 * Copyright (c) 2014. Marshal Chen.
 */

package com.marshalchen.common.ui;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ScrollView;

/**
 * BorderScrollView
 * <ul>
 * <li>onTop and onBottom response ScrollView</li>
 * <li>you can {@link #setOnBorderListener(OnBorderListener)} to set your top and bottom response</li>
 * </ul>
 * 
 * @author trinea@trinea.cn 2013-5-21
 */
public class BorderScrollView extends ScrollView {

    private OnBorderListener onBorderListener;
    private View             contentView;

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

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

    public BorderScrollView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected void onScrollChanged(int x, int y, int oldx, int oldy) {
        super.onScrollChanged(x, y, oldx, oldy);
        doOnBorderListener();
    }

    public void setOnBorderListener(final OnBorderListener onBorderListener) {
        this.onBorderListener = onBorderListener;
        if (onBorderListener == null) {
            return;
        }

        if (contentView == null) {
            contentView = getChildAt(0);
        }
    }

    /**
     * OnBorderListener, Called when scroll to top or bottom
     * 
     * @author <a href="http://www.trinea.cn" target="_blank">Trinea</a> 2013-5-22
     */
    public static interface OnBorderListener {

        /**
         * Called when scroll to bottom
         */
        public void onBottom();

        /**
         * Called when scroll to top
         */
        public void onTop();
    }

    private void doOnBorderListener() {
        if (contentView != null && contentView.getMeasuredHeight() <= getScrollY() + getHeight()) {
            if (onBorderListener != null) {
                onBorderListener.onBottom();
            }
        } else if (getScrollY() == 0) {
            if (onBorderListener != null) {
                onBorderListener.onTop();
            }
        }
    }
}