ListView动态加载数据分页(使用Handler+线程和AsyncTask两种方法)
在android开发中,经常需要使用数据分页,比如要实现一个新闻列表的显示,或者博文列表的显示,不可能第一次加载就展示出全部,这就需要使用分页的方法来加载数据,在android中Handler经常用来在耗时的工作中,它接收子线程发送的数据,并使用数据配合更新UI,AsyncTask是在一个线程中执行耗时操作然后把结果传给UI线程,不需要你亲自去管理线程和句柄。
一、使用Handler+线程方法
1、基础知识
Handler在android系统中,主要负责发送和接收消息,它的用途主要有以下两种:
(1)按照计划来处理一个消息(sendMessage(Message)方法)或者执行某个runnable实例(post(Runnable)方法)
(2)把其他的线程对象放入消息队列中,避免线程冲突。
消息的发送通过post(Runnable), postAtTime(Runnable, long), postDelayed(Runnable, long), sendEmptyMessage(int),sendMessage(Message), sendMessageAtTime(Message, long)和 sendMessageDelayed(Message, long) 方法完成。对于postXXX方法通过Runnable对象给消息队列,并在消息队列到达后被调用。对于sendMessageXXX方法,则传递一个包含message对象,该对象可以被Handler类的handlerMessage(Message)方法处理。
2、主要代码
public class HandlerDemo extends Activity implements OnScrollListener {
private ListView mListView;
LinearLayout loadingLayout;
private Thread mThread;
private ListViewAdapter adapter;
private int startIndex = 1;// 从第1条开始
private int size = 10;// 每次下载十条数据
private List<News> newsList;
List<Map<String, String>> data ;
/*
* 设置布局显示属性
*/
private LayoutParams mLayoutParams = new LayoutParams(
LinearLayout.LayoutParams.WRAP_CONTENT,
LinearLayout.LayoutParams.WRAP_CONTENT);
private LayoutParams ffLayoutParams = new LayoutParams(
LinearLayout.LayoutParams.FILL_PARENT,
LinearLayout.LayoutParams.FILL_PARENT);
private ProgressBar progressBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.news_main);
data=new ArrayList<Map<String, String>>();
addView();
}
private void addView() {
if (startIndex == 1) {
newsList = new ArrayList<News>();
newsList = getNewsList();
}
getdata(newsList);
LinearLayout layout = new LinearLayout(this);
layout.setOrientation(LinearLayout.HORIZONTAL);
progressBar = new ProgressBar(this);
layout.addView(progressBar, mLayoutParams);
TextView textView = new TextView(this);
textView.setText("加载中...");
textView.setGravity(Gravity.CENTER_VERTICAL);
layout.addView(textView, ffLayoutParams);
layout.setGravity(Gravity.CENTER);
loadingLayout = new LinearLayout(this);
loadingLayout.addView(layout, mLayoutParams);
loadingLayout.setGravity(Gravity.CENTER);
// 得到一个ListView用来显示条目
mListView = (ListView) findViewById(R.id.listView);
mListView.addFooterView(loadingLayout);
adapter = new ListViewAdapter();
mListView.setAdapter(adapter);
mListView.setOnScrollListener(this);
mListView.setTextFilterEnabled(true);
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// TODO Auto-generated method stub
if (firstVisibleItem + visibleItemCount == totalItemCount) {
if (mThread == null || !mThread.isAlive()) {
mThread = new Thread() {
@Override
public void run() {
newsList = new ArrayList<News>();
newsList = getNewsList();
getdata(newsList);
Message msg = new Message();
msg.what = 1;
handler.sendMessage(msg);
}
};
mThread.run();
}
}
}
Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
&
补充:移动开发 , Android ,