Android可扩展列表视图示例教程。

1 年 ago
雅, 悟
6 minutes

欢迎来到Android ExpandableListView示例教程。在本教程中，我们将实现一个ExpandableListView，用于按类别对列表数据进行分组。它类似于Android ListView中的菜单和子菜单。

安卓可展开列表

Android的ExpandableListView是一种视图，它以垂直滚动的两级列表显示项目。它与ListView不同之处在于，它允许两级，其中的分组可以通过触摸展开和折叠以进行查看，并且还有它们各自的子项目。在Android中，ExpandableListViewAdapter将数据加载到与该视图相关联的项目中。以下是该类使用的一些重要方法。

  • setChildIndicator(Drawable) : This is used to show an indicator besides each item representing the current state. If the child is the last child for a group, the state state_last will be set
  • setGroupIndicator(Drawable) : An indicator is drawn besides the group representing its state i.e. expanded or collapsed. If the group is empty, the state state_empty will be set. If the group is expanded, the state state_expanded will be set
  • getGroupView() : It returns view for the list group header
  • getChildView() : It returns view for list child item

本类所实现的显著接口如下所示：

  • ExpandableListView.OnChildClickListener : This is overridden to implement the callback method that’s invoked when a child in the expanded list is clicked
  • ExpandableListView.OnGroupClickListener : This is overridden to implement the callback method that’s invoked when a group header in the expanded list is clicked
  • ExpandableListView.OnGroupCollapseListener : It is used for notifying when a group is collapsed
  • ExpandableListView.OnGroupExpandListener : It is used to notify when a group is expanded

安卓可扩展列表视图项目结构

这个项目由三门课程组成。

  • A MainActivity that shows the layout with the ExpandableListView
  • An ExpandableListDataPump which represents a random data in a List and maps the child item data to the respective group headers using a HashMap
  • A CustomExpandableListAdapter which provides the MainActivity with the data from the ExpandableListDataPump class/li>

安卓可扩展列表视图的代码实现

activity_main.xml布局包含一个ExpandableListView在一个RelativeLayout中，如下所示：activity_main.xml

<RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:tools="https://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity">

    <ExpandableListView
        android:id="@+id/expandableListView"
        android:layout_height="match_parent"
        android:layout_width="match_parent"
        android:indicatorLeft="?android:attr/expandableListPreferredItemIndicatorLeft"
        android:divider="@android:color/darker_gray"
        android:dividerHeight="0.5dp" />

</RelativeLayout>

android:indicatorLeft 是一个项目指示器的左边界。注意：除非在XML中明确指定了父项的大小，否则不能对 ExpandableListView 的 android:layout_height 属性使用 wrap_content 值。每个单独列表的组头布局如下所示：list_group.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/listTitle"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingLeft="?android:attr/expandableListPreferredItemPaddingLeft"
        android:textColor="@android:color/black"
        android:paddingTop="10dp"
        android:paddingBottom="10dp" />
</LinearLayout>

子项的布局行在下面给出：list_item.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <TextView
        android:id="@+id/expandedListItem"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:paddingLeft="?android:attr/expandableListPreferredChildPaddingLeft"
        android:paddingTop="10dp"
        android:paddingBottom="10dp" />
</LinearLayout>

定义如下：ExpandableListDataPump类。

package com.Olivia.expandablelistview;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class ExpandableListDataPump {
    public static HashMap<String, List<String>> getData() {
        HashMap<String, List<String>> expandableListDetail = new HashMap<String, List<String>>();

        List<String> cricket = new ArrayList<String>();
        cricket.add("India");
        cricket.add("Pakistan");
        cricket.add("Australia");
        cricket.add("England");
        cricket.add("South Africa");

        List<String> football = new ArrayList<String>();
        football.add("Brazil");
        football.add("Spain");
        football.add("Germany");
        football.add("Netherlands");
        football.add("Italy");

        List<String> basketball = new ArrayList<String>();
        basketball.add("United States");
        basketball.add("Spain");
        basketball.add("Argentina");
        basketball.add("France");
        basketball.add("Russia");

        expandableListDetail.put("CRICKET TEAMS", cricket);
        expandableListDetail.put("FOOTBALL TEAMS", football);
        expandableListDetail.put("BASKETBALL TEAMS", basketball);
        return expandableListDetail;
    }
}

在上述代码中，expandableListDetail对象使用String的ArrayList将组头字符串映射到它们对应的子项上。CustomExpandableListAdapter.java。

package com.Olivia.expandablelistview;

import java.util.HashMap;
import java.util.List;
import android.content.Context;
import android.graphics.Typeface;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.TextView;

public class CustomExpandableListAdapter extends BaseExpandableListAdapter {

    private Context context;
    private List<String> expandableListTitle;
    private HashMap<String, List<String>> expandableListDetail;

    public CustomExpandableListAdapter(Context context, List<String> expandableListTitle,
                                       HashMap<String, List<String>> expandableListDetail) {
        this.context = context;
        this.expandableListTitle = expandableListTitle;
        this.expandableListDetail = expandableListDetail;
    }

    @Override
    public Object getChild(int listPosition, int expandedListPosition) {
        return this.expandableListDetail.get(this.expandableListTitle.get(listPosition))
                .get(expandedListPosition);
    }

    @Override
    public long getChildId(int listPosition, int expandedListPosition) {
        return expandedListPosition;
    }

    @Override
    public View getChildView(int listPosition, final int expandedListPosition,
                             boolean isLastChild, View convertView, ViewGroup parent) {
        final String expandedListText = (String) getChild(listPosition, expandedListPosition);
        if (convertView == null) {
            LayoutInflater layoutInflater = (LayoutInflater) this.context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = layoutInflater.inflate(R.layout.list_item, null);
        }
        TextView expandedListTextView = (TextView) convertView
                .findViewById(R.id.expandedListItem);
        expandedListTextView.setText(expandedListText);
        return convertView;
    }

    @Override
    public int getChildrenCount(int listPosition) {
        return this.expandableListDetail.get(this.expandableListTitle.get(listPosition))
                .size();
    }

    @Override
    public Object getGroup(int listPosition) {
        return this.expandableListTitle.get(listPosition);
    }

    @Override
    public int getGroupCount() {
        return this.expandableListTitle.size();
    }

    @Override
    public long getGroupId(int listPosition) {
        return listPosition;
    }

    @Override
    public View getGroupView(int listPosition, boolean isExpanded,
                             View convertView, ViewGroup parent) {
        String listTitle = (String) getGroup(listPosition);
        if (convertView == null) {
            LayoutInflater layoutInflater = (LayoutInflater) this.context.
                    getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = layoutInflater.inflate(R.layout.list_group, null);
        }
        TextView listTitleTextView = (TextView) convertView
                .findViewById(R.id.listTitle);
        listTitleTextView.setTypeface(null, Typeface.BOLD);
        listTitleTextView.setText(listTitle);
        return convertView;
    }

    @Override
    public boolean hasStableIds() {
        return false;
    }

    @Override
    public boolean isChildSelectable(int listPosition, int expandedListPosition) {
        return true;
    }
}

这个类继承自BaseExpandableListAdapter，并覆盖了基类中的方法，为ExpandableListView提供视图。getView()方法使用给定的索引将数据填充到项的视图中。MainActivity.java文件。

package com.Olivia.expandablelistview;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ExpandableListAdapter;
import android.widget.ExpandableListView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    ExpandableListView expandableListView;
    ExpandableListAdapter expandableListAdapter;
    List<String> expandableListTitle;
    HashMap<String, List<String>> expandableListDetail;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        expandableListView = (ExpandableListView) findViewById(R.id.expandableListView);
        expandableListDetail = ExpandableListDataPump.getData();
        expandableListTitle = new ArrayList<String>(expandableListDetail.keySet());
        expandableListAdapter = new CustomExpandableListAdapter(this, expandableListTitle, expandableListDetail);
        expandableListView.setAdapter(expandableListAdapter);
        expandableListView.setOnGroupExpandListener(new ExpandableListView.OnGroupExpandListener() {

            @Override
            public void onGroupExpand(int groupPosition) {
                Toast.makeText(getApplicationContext(),
                        expandableListTitle.get(groupPosition) + " List Expanded.",
                        Toast.LENGTH_SHORT).show();
            }
        });

        expandableListView.setOnGroupCollapseListener(new ExpandableListView.OnGroupCollapseListener() {

            @Override
            public void onGroupCollapse(int groupPosition) {
                Toast.makeText(getApplicationContext(),
                        expandableListTitle.get(groupPosition) + " List Collapsed.",
                        Toast.LENGTH_SHORT).show();

            }
        });

        expandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
            @Override
            public boolean onChildClick(ExpandableListView parent, View v,
                                        int groupPosition, int childPosition, long id) {
                Toast.makeText(
                        getApplicationContext(),
                        expandableListTitle.get(groupPosition)
                                + " -> "
                                + expandableListDetail.get(
                                expandableListTitle.get(groupPosition)).get(
                                childPosition), Toast.LENGTH_SHORT
                ).show();
                return false;
            }
        });
    }

}

在上面的代码中，我们实现了之前讨论过的所有接口。出于简单起见，我们只会在每次点击时显示一个Toast，其中包含项目的名称或组的状态。但这些可以很容易地修改为执行任何其他操作。下面是我们的应用程序在 Android 可展开列表视图中的操作。注意：ExpandableListViews 本身是可以滚动的。这就结束了 Android ExpandableListView 的教程。

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