Listview动态加载数据

      最近在研究网络数据加载的问题，比如我有几百，甚至上千条数据，这些数据如果一次性全部加载到arraylist，然后再加载到Listview中。我们必然会去单独开线程来做，这样造成的结果就是会出现等待时间很长，用户体验非常不好。我的想法是动态加载数据，第一次加载十条，然后往下面滑动的时候再追加十条，再往下面滑动的时候再去追加，这样大大减少了用户等待的时间，同时给处理数据留下了时间。网上看到了这样一个例子，挺好的，我改动了一下，达到了我想要的结果。

 

package org.developerworks.android;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AbsListView;
import android.widget.BaseAdapter;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.AbsListView.OnScrollListener;
import android.widget.LinearLayout.LayoutParams;

public class ListViewForLoading extends Activity implements OnScrollListener {
	private listViewAdapter adapter = new listViewAdapter();
	ListView listView;
	LinearLayout loadingLayout;
	private Thread mThread;
	/** * 设置布局显示属性 */
	private LayoutParams mLayoutParams = new LinearLayout.LayoutParams(
			LinearLayout.LayoutParams.WRAP_CONTENT,
			LinearLayout.LayoutParams.WRAP_CONTENT);
	/** * 设置布局显示目标最大化属性 */
	private LayoutParams FFlayoutParams = new LinearLayout.LayoutParams(
			LinearLayout.LayoutParams.FILL_PARENT,
			LinearLayout.LayoutParams.FILL_PARENT);
	private ProgressBar progressBar;

	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		init();
	}

	private void init() {
		// TODO Auto-generated method stub
		// 线性布局
		LinearLayout layout = new LinearLayout(this);
		// 设置布局 水平方向
		layout.setOrientation(LinearLayout.HORIZONTAL);
		// 进度条
		progressBar = new ProgressBar(this);
		// 进度条显示位置
		progressBar.setPadding(0, 0, 15, 0);
		// 把进度条加入到layout中
		layout.addView(progressBar, mLayoutParams);
		// 文本内容
		TextView textView = new TextView(this);
		textView.setText("加载中...");
		textView.setGravity(Gravity.CENTER_VERTICAL);
		// 把文本加入到layout中
		layout.addView(textView, FFlayoutParams);
		// 设置layout的重力方向，即对齐方式是
		layout.setGravity(Gravity.CENTER);
		// 设置ListView的页脚layout
		loadingLayout = new LinearLayout(this);
		loadingLayout.addView(layout, mLayoutParams);
		loadingLayout.setGravity(Gravity.CENTER);
		// 得到一个ListView用来显示条目
		listView = (ListView) findViewById(R.id.tv);
		// 添加到脚页显示
		listView.addFooterView(loadingLayout);
		// 给ListView添加适配器
		listView.setAdapter(adapter);
		// 给ListView注册滚动监听
		listView.setOnScrollListener(this);
	}

	/**
	 * 要用用于生成显示数据
	 * 
	 * @author huangbq
	 */
	class listViewAdapter extends BaseAdapter {
		int count = 10;

		public int getCount() {
			return count;
		}

		public Object getItem(int pos) {
			return pos;
		}

		public long getItemId(int pos) {
			return pos;
		}

		public View getView(int pos, View v, ViewGroup p) {
			TextView view;
			if (v == null) {
				view = new TextView(ListViewForLoading.this);
			} else {
				view = (TextView) v;
			}
			view.setText("ListItem " + pos);
			view.setTextSize(20f);
			view.setGravity(Gravity.CENTER);
			view.setHeight(60);
			return view;
		}
	}

	@Override
	public void onScroll(AbsListView view, int firstVisibleItem,
			int visibleItemCount, int totalItemCount) {
		// TODO Auto-generated method stub
		if (firstVisibleItem + visibleItemCount == totalItemCount) {
			// 开线程去下载网络数据
			if (mThread == null || !mThread.isAlive()) {
				mThread = new Thread() {
					@Override
					public void run() {
						try {
							// 这里放你网络数据请求的方法，我在这里用线程休眠5秒方法来处理
							Thread.sleep(5000);
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
						Message message = new Message();
						message.what = 1;
						handler.sendMessage(message);
					}
				};
				mThread.start();
			}
		}
	}

	@Override
	public void onScrollStateChanged(AbsListView view, int scrollState) {
		// TODO Auto-generated method stub
	}

	private Handler handler = new Handler() {
		@Override
		public void handleMessage(Message msg) {
			// TODO Auto-generated method stub
			switch (msg.what) {
			case 1:
				if (adapter.count <= 41) {
					adapter.count += 10;
					int currentPage = adapter.count / 10;
					Toast.makeText(getApplicationContext(),
							"第" + currentPage + "页", Toast.LENGTH_LONG).show();
				} else {
					listView.removeFooterView(loadingLayout);
				}
				// 重新刷新Listview的adapter里面数据
				adapter.notifyDataSetChanged();
				break;
			default:
				break;
			}
		}
	};
}

 

main.xml别忘了加这段了

 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
	android:layout_width="wrap_content"
    android:layout_height="wrap_content">
    <ListView android:id="@+id/tv" 
    	android:layout_width="wrap_content" 
    	android:layout_height="wrap_content"/>
</LinearLayout>