Android学习笔记（二）——两个ListView联动

最近一直在看项目，进行一些UI上更改，改了几个前辈遗留的bug，看到一个页面的左右两个ListView只有单方面的联动，即左边的ListVive点击可以让右边的ListView定位到相应的位置，而右边的ListView滑动并不能改变左边的ListView，虽然产品大哥没有提这个bug，但是我有强迫症啊，我也很绝望啊，就动手改呗。希望达到的效果呢就是普遍在外卖软件上可以看到的，左边是商品类型，右边是商品类型和具体商品的多布局，点击左边ListView，右边可以定位到对应的商品类型；右边ListView滑动时，当商品类型改变时，左边的ListView也定位到对应的商品类型。思路应该是简单的，左对右实现起来很简单，  对左边的ListView设置item点击监听，setOnItemClickListener()，找到点击的item的商品类型在右边ListView中的position，然后右边ListView调用setSelection(position)方法即可；右边对左边的联动就要对右边ListView进行滑动监听，setOnScrollListener()，重写onScroll()方法，处理方法与上面的类似，但是我遇到了一个问题，判断条件为第一个可见item是否为商品类型并找出左边对应的位置，我是这样写的

@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
String title = rightListAdapter.getItem(firstVisibleItem).toString();
int section = leftListAdapter.indexOf(title);
if (section == -1) return;
leftListView.setItemChecked(section, true);
leftListView.smoothScrollToPosition(section);
}
但是呢出现了一个问题，当右边的第一个条目为商品类型时，左边的ListView不能滑动，或者说是滑动了，但是又被定位到右边商品类型所对应的左边的位置，打断点发现，即使触摸区域在左边的ListView范围，还是会走右边ListView的onScroll()方法。语言表达可能不准确，有兴趣可以自己试一下。我的解决方法呢就是设置一个标志位，当右边的ListView的滚动状态为停止的时候就不去执行onScroll()里的代码。所以代码就变成了这样。
rightListView.setOnScrollListener(new AbsListView.OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {
shouldSet = false;
} else {
shouldSet = true;
}
}

@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
if (shouldSet){
String title = rightListAdapter.getItem(firstVisibleItem).toString();
int section = leftListAdapter.indexOf(title);
if (section == -1) return;
leftListView.setItemChecked(section, true);
leftListView.smoothScrollToPosition(section);
}
}
});
好了 就是这样！

下面是MainActivity的代码，demo戳这里。

package com.ccc.listviewlinkage;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.View;import android.widget.AbsListView;import android.widget.AdapterView;import android.widget.ListView;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {    private ListView leftListView;    private ListView rightListView;    private LeftListAdapter leftListAdapter;    private RightListAdapter rightListAdapter;    private List<String> leftList;    private List<GoodsBean> rightList;    private boolean isScroll;    private boolean shouldSet;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initData();        initViews();    }    private void initData() {        leftList = new ArrayList<>();        rightList = new ArrayList<>();        for (int i = 0; i < 10; i++) {            leftList.add("商品类型 " + i);        }        for (int i = 0; i < 10; i++) {            rightList.add(new GoodsBean("商品类型 " + i, 0));            for (int i1 = 0; i1 < 10; i1++) {                rightList.add(new GoodsBean("商品名称 " + i1, 1));            }        }    }    private void initViews() {        leftListView = (ListView) findViewById(R.id.left_list_view);        rightListView = (ListView) findViewById(R.id.right_list_view);        leftListAdapter = new LeftListAdapter(this, leftList);        leftListView.setAdapter(leftListAdapter);        rightListAdapter = new RightListAdapter(this, rightList);        rightListView.setAdapter(rightListAdapter);        leftListView.setItemChecked(0, true);        leftListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {            @Override            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {                isScroll = false;                leftListView.setItemChecked(position, true);                int section = rightListAdapter.indexOf(leftListAdapter.getItem(position).toString());                if (section == -1) return;                rightListView.setSelection(section);            }        });        rightListView.setOnScrollListener(new AbsListView.OnScrollListener() {            @Override            public void onScrollStateChanged(AbsListView view, int scrollState) {                if (scrollState == AbsListView.OnScrollListener.SCROLL_STATE_IDLE) {                    shouldSet = false;                } else {                    shouldSet = true;                }            }            @Override            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {                if (isScroll){                    if (shouldSet){                        String title = rightListAdapter.getItem(firstVisibleItem).toString();                        int section = leftListAdapter.indexOf(title);                        if (section == -1) return;                        leftListView.setItemChecked(section, true);                        leftListView.smoothScrollToPosition(section);                    }                } else {                    isScroll = true;                }            }        });    }}