Android中包含Header和Footer的无限ListView的实现

原：

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 java.util.ArrayList;
import java.util.List;
 
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);
 
		List list = new ArrayList();
		for (int i = 0; i < 10; i++) {
			String text = "text-" + i;
			list.add(text);
		}
 
		ListView listView = (ListView) findViewById(R.id.listview_main);
		StringAdapter adapter = new StringAdapter(this, list, 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.List;
 
import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.widget.BaseAdapter;
import android.widget.ListView;
 
/**
 *
 *
 * @author wubotao
 *
 * @param
 *            被存放元素的类型
 *
 *
 */
public abstract class AbstractAdapter extends BaseAdapter {
 
	protected Context context;
 
	protected List list;
 
	protected ListView listView;
 
	protected AbstractAdapter(Context context, List list, ListView listView) {
		this.context = context;
		this.list = list;
		this.listView = listView;
 
		init();
	}
 
	/**
	 * 数据和用户界面初始化
	 */
	public abstract void init();
 
	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 {
 
	boolean headerLoading = false;
	boolean footerLoading = false;
 
	ViewSwitcher footerView;
	ViewSwitcher headerView;
 
	public StringAdapter(Context context, List list, ListView listView) {
		super(context, list, listView);
	}
 
	@Override
	public void init() {
		LayoutInflater inflater = LayoutInflater.from(context);
 
		headerView = (ViewSwitcher) inflater.inflate(R.layout.header, null);
		listView.addHeaderView(headerView);
 
		footerView = (ViewSwitcher) inflater.inflate(R.layout.footer, null);
		listView.addFooterView(footerView);
 
		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> {
 
		@Override
		protected void onPreExecute() {
			headerLoading = true;
			headerLoading(true);
		}
 
		@Override
		protected List doInBackground(String... params) {
			List list = new ArrayList();
			try {
				Thread.sleep(5000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			for (int i = 0; i < 10; i++) {
				list.add("header-" + i);
			}
			return list;
		}
 
		@Override
		protected void onPostExecute(List result) {
			list.addAll(0, result);
			notifyDataSetChanged();
 
			headerLoading = false;
			headerLoading(false);
		}
 
	}
 
	class FooterTask extends AsyncTask> {
 
		@Override
		protected void onPreExecute() {
			footerLoading = true;
			footerLoading(true);
		}
 
		@Override
		protected List doInBackground(String... params) {
			List messages = new ArrayList();
			try {
				Thread.sleep(5000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			for (int i = 0; i < 10; i++) {
				list.add("header-" + i);
			}
			return messages;
		}
 
		@Override
		protected void onPostExecute(List result) {
			list.addAll(result);
			notifyDataSetChanged();
 
			footerLoading = false;
			footerLoading(false);
		}
 
	}
 
	private void footerLoading(boolean isLoading) {
		if (isLoading) {
			footerView.setDisplayedChild(1);
		} else {
			footerView.setDisplayedChild(0);
		}
	}
 
	private void headerLoading(boolean isLoading) {
		if (isLoading) {
			headerView.setDisplayedChild(1);
		} else {
			headerView.setDisplayedChild(0);
		}
	}
 
}