【Android】ListView监听上下滑动（判断是否显示返回顶部按钮

设置滚动监听判断ListView的滚动方向同时获取屏幕高度、ListView实际高度，判断是否需要展示返回顶部按钮

package com.zihao.activity;

 

import java.util.ArrayList;

import java.util.List;

 

import com.zihao.adapter.MyAdapter;

import com.zihao.utils.ScreenUtil;

 

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.AbsListView;

import android.widget.AbsListView.OnScrollListener;

import android.widget.Button;

import android.widget.ListView;

import android.app.Activity;

 

/**

 * 主界面

 *

 * @author zihao

 * @details 因为有些手机是有虚拟按键的（在计算屏幕分辨率的时候，有些可以去除掉虚拟区域的区域->如三星，有些不行->如MX3），为了计算的准确性，

 *          各位可以设置Activity为Theme

 *          .NoTitleBar.Fullscreen填满屏幕(解决类似MX3这种在计算过程中把虚拟键盘算入屏幕高度的)。

 */

public class MainActivity extends Activity implements OnClickListener {

 

    private ListView listView;// List数据列表

    private Button toTopBtn;// 返回顶部的按钮

    private MyAdapter adapter;

    private boolean scrollFlag = false;// 标记是否滑动

    private int lastVisibleItemPosition = 0;// 标记上次滑动位置

 

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

 

        initView();

    }

 

    /**

     * 初始化视图

     */

    private void initView() {

        listView = (ListView) findViewById(R.id.my_listView);

        toTopBtn = (Button) findViewById(R.id.top_btn);

 

        adapter = new MyAdapter(this, getTitleDatas());

        listView.setAdapter(adapter);

 

        toTopBtn.setOnClickListener(this);

        listView.setOnScrollListener(new OnScrollListener() {

 

            @Override

            public void onScrollStateChanged(AbsListView view, int scrollState) {

                // TODO Auto-generated method stub

                switch (scrollState) {

                // 当不滚动时

                case OnScrollListener.SCROLL_STATE_IDLE:// 是当屏幕停止滚动时

                    scrollFlag = false;

                    // 判断滚动到底部

                    if (listView.getLastVisiblePosition() == (listView

                            .getCount() - 1)) {

                        toTopBtn.setVisibility(View.VISIBLE);

                    }

                    // 判断滚动到顶部

                    if (listView.getFirstVisiblePosition() == 0) {

                        toTopBtn.setVisibility(View.GONE);

                    }

 

                    break;

                case OnScrollListener.SCROLL_STATE_TOUCH_SCROLL:// 滚动时

                    scrollFlag = true;

                    break;

                case OnScrollListener.SCROLL_STATE_FLING:// 是当用户由于之前划动屏幕并抬起手指，屏幕产生惯性滑动时

                    scrollFlag = false;

                    break;

                }

            }

 

            /**

             * firstVisibleItem：当前能看见的第一个列表项ID（从0开始）

             * visibleItemCount：当前能看见的列表项个数（小半个也算） totalItemCount：列表项共数

             */

            @Override

            public void onScroll(AbsListView view, int firstVisibleItem,

                    int visibleItemCount, int totalItemCount) {

                // 当开始滑动且ListView底部的Y轴点超出屏幕最大范围时，显示或隐藏顶部按钮

                if (scrollFlag

                        && ScreenUtil.getScreenViewBottomHeight(listView) >= ScreenUtil

                                .getScreenHeight(MainActivity.this)) {

                    if (firstVisibleItem > lastVisibleItemPosition) {// 上滑

                        toTopBtn.setVisibility(View.VISIBLE);

                    } else if (firstVisibleItem < lastVisibleItemPosition) {// 下滑

                        toTopBtn.setVisibility(View.GONE);

                    } else {

                        return;

                    }

                    lastVisibleItemPosition = firstVisibleItem;

                }

            }

        });

    }

 

    /**

     * 获取标题数据列表

     *

     * @return

     */

    private List<string> getTitleDatas() {

        List<string> titleArray = new ArrayList<string>();

        for (int i = 0; i < 30; i++) {

            titleArray.add("这是第" + i + "个item");

        }

        return titleArray;

    }

 

    /**

     * 滚动ListView到指定位置

     *

     * @param pos

     */

    private void setListViewPos(int pos) {

        if (android.os.Build.VERSION.SDK_INT >= 8) {

            listView.smoothScrollToPosition(pos);

        } else {

            listView.setSelection(pos);

        }

    }

 

    @Override

    public void onClick(View v) {

        // TODO Auto-generated method stub

        switch (v.getId()) {

        case R.id.top_btn:// 点击按钮返回到ListView的第一项

            setListViewPos(0);

            break;

        }

    }

 

}</string></string></string>

 

来源：