在Android上实现树形控件

  在PC上我们已经习惯了树形控件，因为其可以清晰的展现各个节点之间的层次结果，但是在Android平台上，系统并没有提供这样一个控件，而是只有ListView。不过通过改写改写与ListView绑定的Adapter可以实现这样一个效果。

  一个ListView需要和一个Adapter绑定，用于管理数据。在这里以BaseAdapter为例，继承Adapter需要重写四个函数，其中较为重要的是两个：

   1 public int getCount()；//该函数返回ListView 的ListItem的条数

   2 public View getView(int position, View view, ViewGroup arg2)//负责绘制每一个item。如果getCount（）返回10，那么getView（）就会被调用10次。

首先开发自己的数据结构：

package bupt.liyazhou.ui;

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

/*
 * @ author:liyazhou
 * @date:2013.4.29
 * @description:Node类用来在UI层中存储一个节点的信息
 *
 */
public class Node {
	private Node parent=null;//父节点
	private List<Node> children=null;
	private String oid=null;//该节点的oid
	private String name=null;//该节点信息的描述
	private String value=null;//该节点的值
	private boolean isLeaf=false;//是否为叶节点
	private boolean isExpanded=false;//该节点是否展开
	private int icon=-1;//该节点的图标对应的id
	private int iconForExpandedOrFolded=-1;
	private int iconForExpanding=-1;
	private int iconForFolding=-1;
	private boolean tableItemOrNot=false;//表示是否为表结构的一列

	public Node(Node parent,String oid,String description,boolean isLeaf,int icon,int exIcon,int foIcon)
	{
		this.parent=parent;
		this.oid=oid;
		this.name=description;
		this.isLeaf=isLeaf;
		this.icon=icon;
		this.iconForExpanding=exIcon;
		this.iconForFolding=foIcon;
	}
	public void setTableItemOrNot(boolean tableItemOrNot)
	{
		this.tableItemOrNot=tableItemOrNot;
	}
	public boolean getTableItemOrNot()
	{
		return this.tableItemOrNot;
	}
	//设置value
	public void setValue(String value)
	{
		this.value=value;
	}
	//得到value
	public String getValue()
	{
		return this.value;
	}
	//设置图标
	public void setIcon(int icon)
	{
		this.icon=icon;
	}
	public int getIcon()
	{
		return this.icon;
	}
	//得到description
	public String getDescription()
	{
		return this.name;
	}
	//得到oid
	public String getOid()
	{
		return this.oid;
	}
	//得到是否为叶节点
	public boolean isLeafOrNot()
	{
		return this.isLeaf;
	}
	//得到当前节点所在的层数，根为0层
	public int getLevel()
	{
		return parent==null?0:parent.getLevel()+1;
	}
	//设置是否展开
	public void setExpanded(boolean isExpanded)
	{
		this.isExpanded=isExpanded;
	}
	public boolean getExpanded()
	{
		return this.isExpanded;
	}
	//添加子节点
	public void addChildNode(Node child)
	{
		if(this.children==null)
		{
			this.children=new ArrayList<Node>();
		}
		this.children.add(child);
	}
	//清空子节点
	public void clearChildren()
	{
		if(!this.children.equals(null))
		{
			this.children.clear();
		}
	}
	//是否为根节点
	public boolean isRoot()
	{
		return this.parent.equals(null)?true:false;
	}
    //设置展开图标
	public void setExpandIcon(int expand)
	{
		this.iconForExpanding=expand;
	}
	//设置折叠图标
	public void setFoldIcon(int fold)
	{
		this.iconForFolding=fold;
	}
	//得到展开或折叠图标
	public int getExpandOrFoldIcon()
	{
		if(this.isExpanded==true)
			return this.iconForExpanding;
		else
			return this.iconForFolding;
	}
	//得到子树
	public List<Node> getChildren()
	{
		return this.children;
	}
}

然后写自己的Adapter

package bupt.liyazhou.ui;

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

import android.R;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

public class MibTreeListAdapter extends BaseAdapter {
	private Context context=null;
	private List<Node> nodeList=new ArrayList<Node> ();//所有的节点
	private List<Node> nodeListToShow=new ArrayList<Node>();//要展现的节点
    private LayoutInflater inflater=null;
    private Node root=null;

    public MibTreeListAdapter(Context con,Node Root,int layout)
    {
    	this.context=con;
    	this.inflater=(LayoutInflater)con.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    	establishNodeList(Root);
    	this.root=Root;
    	setNodeListToShow();
    }
    public void establishNodeList(Node node)
    {
    	nodeList.add(node);
    	if(node.isLeafOrNot())
    		return;
    	List<Node> children=node.getChildren();
    	for(int i=0;i<children.size();i++)
    	{
    		establishNodeList(children.get(i));
    	}
    }
    public void setNodeListToShow()
    {
    	this.nodeListToShow.clear();
    	establishNodeListToShow(this.root);
    }

    //构造要展示在listview的nodeListToShow
    public void establishNodeListToShow(Node node)
    {
    	this.nodeListToShow.add(node);
    	if(node.getExpanded()&&!node.isLeafOrNot()&&node.getChildren()!=null)
    	{
    		List<Node> children=node.getChildren();
    		for(int i=0;i<children.size();i++)
    		{
    			establishNodeListToShow(children.get(i));
    		}
    	}
    }

    //根据oid得到某一个Node,并更改其状态
    public void changeNodeExpandOrFold(int position)
    {
    	String oid=this.nodeListToShow.get(position).getOid();
    	for(int i=0;i<this.nodeList.size();i++)
    	{
    		if(nodeList.get(i).getOid().equals(oid))
    		{
    			boolean flag=nodeList.get(i).getExpanded();
    			nodeList.get(i).setExpanded(!flag);
    		}

    	}
    }

    //listItem被点击的响应事件
    public Node OnListItemClick(int position)
    {
    	Node node=this.nodeListToShow.get(position);
    	if(node.isLeafOrNot())
    	{
    		//处理snmp代码
    		Toast.makeText(this.context, "该节点为子节点", Toast.LENGTH_SHORT).show();
    		return node;
    	}
    	else
    	{
    		this.changeNodeExpandOrFold(position);
    		this.setNodeListToShow();
    		this.notifyDataSetChanged();
    		return null;
    	}
    }
	public int getCount() {
		// TODO Auto-generated method stub
		return nodeListToShow.size();
	}

	public Object getItem(int arg0) {
		// TODO Auto-generated method stub
		return nodeListToShow.get(arg0);
	}

	public long getItemId(int arg0) {
		// TODO Auto-generated method stub
		return arg0;
	}

	public View getView(int position, View view, ViewGroup parent) {
		// TODO Auto-generated method stub
		Holder holder=null;
		if(view!=null)
		{
			holder=(Holder)view.getTag();
		}
		else
		{
			holder=new Holder();
			view=this.inflater.inflate(bupt.liyazhou.R.layout.listview_item, null);
			holder.description=(TextView)view.findViewById(bupt.liyazhou.R.id.textview_nodeDescription);
			holder.nodeIcon=(ImageView)view.findViewById(bupt.liyazhou.R.id.imageview_nodeImage);
			holder.expandOrFoldIcon=(ImageView)view.findViewById(bupt.liyazhou.R.id.imageview_expandedImage);
			view.setTag(holder);
		}

		//绘制一个item

		//设置文字
		Node node= this.nodeListToShow.get(position);
		holder.description.setText(node.getDescription());

		//设置图标
		int icon=node.getIcon();
		if(icon!=-1)
		{
			holder.nodeIcon.setImageResource(icon);
			holder.nodeIcon.setVisibility(View.VISIBLE);
		}
		else
			holder.nodeIcon.setVisibility(View.INVISIBLE);

		//设置展开折叠图标
		if(!node.isLeafOrNot())
		{
		  int expandIcon=node.getExpandOrFoldIcon();
		  if(expandIcon==-1)
			  holder.expandOrFoldIcon.setVisibility(View.INVISIBLE);
		  else
		  {
			  holder.expandOrFoldIcon.setImageResource(expandIcon);
			  holder.expandOrFoldIcon.setVisibility(View.VISIBLE);
		  }

		}
		else
		{
			holder.expandOrFoldIcon.setVisibility(View.INVISIBLE);
		}
		view.setPadding(node.getLevel()*35, 10, 10, 10);
		return view;
	}

	public class Holder
	{
		TextView description;
		ImageView nodeIcon;
		ImageView expandOrFoldIcon;
	}

}

listview_item.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    <ImageView
       android:id="@+id/imageview_nodeImage"
       android:layout_height="fill_parent"
       android:layout_width="wrap_content"
       android:layout_alignParentLeft="true"
       android:paddingRight="10dp"/>
    <TextView
        android:id="@+id/textview_nodeDescription"
        android:layout_height="fill_parent"
        android:layout_width="wrap_content"
        android:layout_toRightOf="@id/imageview_nodeImage"
        />
    <ImageView
        android:id="@+id/imageview_expandedImage"
        android:layout_height="fill_parent"
        android:layout_width="wrap_content"
        android:layout_alignParentRight="true"/>

</RelativeLayout>

实现效果：