Android中包含Header和Footer的无限ListView的实现

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/