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/