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。

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;
}
}

};
}

运行结果如下图：







分类:
android listview研究