Android——基本控件（下）（二十）

1. 树型组件：ExpandableListView

1.1 知识点

（1）掌握树型组件的定义；

（2）可以使用事件对树操作进行监听。

2. 具体内容

既然这个组件可以完成列表的功能，肯定就需要一个可以操作的数据，那么这里也是使用setAdapter()这个方法完成数据的设置，可以大家可以发现，setAdapter方法中可以接受数据类型：

public void setAdapter(ExpandableListAdapter adapter) 

发现如果想要设置数据，必须要一个ExpandaableListAdapter这个接口对象。常用的实现类就是BaseExpandableListAdapter，如果要设置数据，那么必须要写一个适配器类集成BaseExpandableListAdapter这个抽象类。

定义一个适配器类。

package com.example.expandablelistview;

import android.content.Context;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseExpandableListAdapter;
import android.widget.FrameLayout.LayoutParams;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MyBaseExpandableListAdapter extends BaseExpandableListAdapter {
	private String[] groups = {"我的好友","家人","同事","同学","黑名单"};
	private String[][] child = {
   
   {"张三","李四"},{"父亲","母亲"},{"朱六","张鹏程"},{"王五","赵六"},{"票贩子","推销"}};
	private Context context;
	public MyBaseExpandableListAdapter(Context  context){
		this.context = context;
	}
	@Override
	public Object getChild(int groupPosition, int childPosition) {//取得指定的子项
		return this.child[groupPosition][childPosition];
	}

	@Override
	public long getChildId(int groupPosition, int childPosition) {//取得子项ID
		return childPosition;
	}
	public  TextView bulidTextView(){//自定义方法，建立文本
		TextView textView = new TextView(this.context);
		LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,35);//指定布局参数
		textView.setLayoutParams(params);
		textView.setTextSize(15.0f);
		textView.setGravity(Gravity.LEFT);
		textView.setPadding(10,10,10,10);//设置内边距
		return textView ;
	}

	@Override
	public View getChildView(int groupPosition, int childPosition,
			boolean isLastChild, View convertView, ViewGroup parent) {//返回子项组件
		TextView textView = this.bulidTextView();
		textView.setText(getChild(groupPosition,childPosition).toString());//设置内容
		return textView;
	}

	@Override
	public int getChildrenCount(int groupPosition) {//取得子项个数
		return this.child[groupPosition].length;
	}

	@Override
	public Object getGroup(int groupPosition) {//返回组对象
		return this.groups[groupPosition];
	}

	@Override
	public int getGroupCount() {//返回组个数
		return this.groups.length;
	}

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

	@Override
	public View getGroupView(int groupPosition, boolean isExpanded,
			View convertView, ViewGroup parent) {
		TextView textView = this.bulidTextView();
		textView.setText(this.getGroup(groupPosition).toString());
		return textView;
	}

	@Override
	public boolean hasStableIds() {//
		return true;
	}

	@Override
	public boolean isChildSelectable(int groupPosition, int childPosition) {
		return true;
	}

}

现在我们适配器类已经完成了，此时需要定义一个专门的组件去填充数据，这个组件就需要在布局中完成。

<LinearLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <ExpandableListView
        android:id="@+id/mylistView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
</LinearLayout>

现在的关键还是在Activity程序的编写。

package com.example.expandablelistview;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ExpandableListAdapter;
import android.widget.ExpandableListView;
import android.widget.ExpandableListView.OnChildClickListener;
import android.widget.ExpandableListView.OnGroupClickListener;
import android.widget.ExpandableListView.OnGroupCollapseListener;
import android.widget.ExpandableListView.OnGroupExpandListener;
import android.widget.Toast;

public class ExpandableListViewActivity extends Activity {
	private ExpandableListView mylistView = null;
	private ExpandableListAdapter adapter = null;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		super.setContentView(R.layout.activity_expandable_list_view);
		this.mylistView = (ExpandableListView) super.findViewById(R.id.mylistView);
		this.adapter = new MyBaseExpandableListAdapter(this);
		this.mylistView.setAdapter(this.adapter);//设置数据
		//此时我们的组件显示就已经完成，其实组件的显示意义似乎不是很大，肯定要跟上事件处理
		
		this.mylistView.setOnChildClickListener(new OnChildClickListener(){//设置子节点单击事件
			@Override
			public boolean onChildClick(ExpandableListView parent, View v,
					int groupPosition, int childPosition, long id) {
				Toast.makeText(ExpandableListViewActivity.this, "子菜单被单击，组：" +groupPosition +",子：" + childPosition  , Toast.LENGTH_SHORT).show();
				return false;
			}
			
		});
		this.mylistView.setOnGroupClickListener(new OnGroupClickListener(){//设置组单击事件

			@Override
			public boolean onGroupClick(ExpandableListView parent, View v,
					int groupPosition, long id) {
				Toast.makeText(ExpandableListViewActivity.this, "组被单击了" , Toast.LENGTH_SHORT).show();
				return false;
			}
			
		});
		this.mylistView.setOnGroupCollapseListener(new OnGroupCollapseListener(){//菜单组关闭事件

			@Override
			public void onGroupCollapse(int groupPosition) {
				Toast.makeText(ExpandableListViewActivity.this, "组关闭" , Toast.LENGTH_SHORT).show();
				
			}
			
		});
		this.mylistView.setOnGroupExpandListener(new OnGroupExpandListener(){//菜单组打开事件

			@Override
			public void onGroupExpand(int groupPosition) {
				Toast.makeText(ExpandableListViewActivity.this, "组打开" , Toast.LENGTH_SHORT).show();
			}
			
		});
		this.mylistView.setOnItemClickListener(new OnItemClickListener(){//单击子项

			@Override
			public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
					long arg3) {
				Toast.makeText(ExpandableListViewActivity.this, "子项单击" , Toast.LENGTH_SHORT).show();
			}
		});
		
	}
}

关键的问题还是在数据的设置上。

1.3 小结

（1）使用ExpandableListView可以完成数据的分组显示；

（2）ExpandableListView组件的分组及子项都可以监听并进行相应处理。