Android中包含Header和Footer的无限ListView的实现

Posted 2022-08-15 jdsjlzx

android如果ListView不需要通过点击Header或者Footer来增加新数据，那还比较简单。有一种情况是需要通过点击Header和Footer来向ListView中添加新的数据，这在理论上就是可以包含无限元素的ListView。

我在经历的两个项目中都遇到过这种情况，在做第一个项目时，因为经验不足，走了很多弯路，写出来的代码也相当复杂。在我做第二个项目的时候，我对前一次的代码进行了优化，在满足要求和性能的同时，代码量大大减少。

下面就是包含Header和Footer的无限ListView的一个实现，通过点击Header或者Footer，可以向ListView中添加数据，这是第一个版本。

1. MainActivity.java
MainActivity的作用是显示主界面的ListView。

package com.wubotao.activity;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;

import com.wubotao.adapter.StringAdapter;

public class MainActivity extends Activity 
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) 
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main_list);

    ListView listView = (ListView) findViewById(R.id.listview_main);
    StringAdapter adapter = new StringAdapter(this, listView);
    listView.setAdapter(adapter);

  

2. AbstractAdapter.java
AbstractAdapter是一个抽象类，实现了BaseAdapter的部分方法。

package com.wubotao.adapter;

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

import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.widget.BaseAdapter;
import android.widget.ListView;

/**
 * 
 * 
 * @author wubotao
 * 
 * @param <T>
 *            被存放元素的类型
 * 
 * 
 */
public abstract class AbstractAdapter<T> extends BaseAdapter 

  protected Context context;

  protected List<T> list = new ArrayList<T>();

  protected ListView listView;

  protected AbstractAdapter(Context context, ListView listView) 
    this.context = context;
    this.listView = listView;
  

  public int getCount() 
    return list == null ? 0 : list.size();
  

  public Object getItem(int position) 
    return list.get(position);
  

  public long getItemId(int position) 
    return position;
  

  protected Handler handler = new Handler() 
    @Override
    public void handleMessage(Message msg) 
      notifyDataSetChanged();
    
  ;

3. StringAdapter.java
StringAdapter继承自AbstractAdapter，主要作用是实现数据和ListView图形界面的交互。

package com.wubotao.adapter;

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

import android.content.Context;
import android.os.AsyncTask;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.ViewSwitcher;

import com.wubotao.activity.R;

/**
 * 
 * 
 * @author wubotao
 * 
 */
public class StringAdapter extends AbstractAdapter<String> 

  boolean headerLoading = false;
  boolean footerLoading = false;

  ViewSwitcher footerView;
  ViewSwitcher headerView;

  public StringAdapter(Context context, ListView listView) 
    super(context, listView);

    LayoutInflater inflater = LayoutInflater.from(context);

    headerView = (ViewSwitcher) inflater.inflate(R.layout.header, null);
    listView.addHeaderView(headerView);
    headerLoading(true);

    footerView = (ViewSwitcher) inflater.inflate(R.layout.footer, null);

    new ContentTask().execute();

    TextView moreByHeader = (TextView) headerView
        .findViewById(R.id.textview_to_load_more);
    moreByHeader.setOnClickListener(new View.OnClickListener() 
      @Override
      public void onClick(View v) 
        if (!headerLoading) 
          new HeaderTask().execute();
        
      
    );

    TextView moreByFooter = (TextView) footerView
        .findViewById(R.id.textview_to_load_more);
    moreByFooter.setOnClickListener(new View.OnClickListener() 
      @Override
      public void onClick(View v) 
        if (!footerLoading) 
          new FooterTask().execute();
        
      
    );
  

  @Override
  public View getView(int position, View convertView, ViewGroup parent) 
    ViewHolder viewHolder;
    if (convertView == null) 
      viewHolder = new ViewHolder();
      LayoutInflater inflater = LayoutInflater.from(context);
      convertView = inflater.inflate(R.layout.main_list_item, null);
      viewHolder.content = (TextView) convertView
          .findViewById(R.id.textview_content);
      convertView.setTag(viewHolder);
     else 
      viewHolder = (ViewHolder) convertView.getTag();
    

    String text = (String) getItem(position);
    viewHolder.content.setText(text);

    return convertView;
  

  class ViewHolder 
    TextView content;
  

  class HeaderTask extends AsyncTask<String, Integer, List<String>> 

    @Override
    protected void onPreExecute() 
      headerLoading(true);
    

    @Override
    protected List<String> doInBackground(String... params) 
      List<String> list = new ArrayList<String>();
      try 
        Thread.sleep(1000);
       catch (InterruptedException e) 
        e.printStackTrace();
      
      for (int i = 0; i < 3; i++) 
        list.add("header-" + i);
      
      return list;
    

    @Override
    protected void onPostExecute(List<String> result) 
      list.addAll(0, result);
      notifyDataSetChanged();

      headerLoading(false);
    

  

  class ContentTask extends AsyncTask<String, Integer, List<String>> 

    @Override
    protected List<String> doInBackground(String... params) 
      List<String> list = new ArrayList<String>();
      for (int i = 0; i < 3; i++) 
        list.add("content-" + i);
      

      try 
        Thread.sleep(1000);
       catch (InterruptedException e) 
        e.printStackTrace();
      

      return list;
    

    @Override
    protected void onPostExecute(List<String> result) 
      list.addAll(0, result);
      notifyDataSetChanged();

      headerLoading(false);
      listView.addFooterView(footerView);
    

  

  class FooterTask extends AsyncTask<String, Integer, List<String>> 

    @Override
    protected void onPreExecute() 
      footerLoading(true);
    

    @Override
    protected List<String> doInBackground(String... params) 
      List<String> messages = new ArrayList<String>();
      try 
        Thread.sleep(1000);
       catch (InterruptedException e) 
        e.printStackTrace();
      
      for (int i = 0; i < 3; i++) 
        list.add("footer-" + i);
      
      return messages;
    

    @Override
    protected void onPostExecute(List<String> result) 
      list.addAll(result);
      notifyDataSetChanged();

      footerLoading(false);
    

  

  private void footerLoading(boolean isLoading) 
    if (isLoading) 
      footerView.setDisplayedChild(1);
     else 
      footerView.setDisplayedChild(0);
    
    footerLoading = isLoading;
  

  private void headerLoading(boolean isLoading) 
    if (isLoading) 
      headerView.setDisplayedChild(1);
     else 
      headerView.setDisplayedChild(0);
    
    headerLoading = isLoading;
  

里面有一些XML在博客上没法显示，SVN源码下载：https://open-source-project-home.googlecode.com/svn/trunk/EndlessListView/