Android ListView 滚动翻页效果——加载更多

前面说过了ListView的下拉刷新效果，有些时候我们需要让ListView在滑动到最底部时，自动去向服务器请求下一页数据。这时候就需要监听的ListView的滑动状态了。

mListView.setOnScrollListener(OnScrollListener l);

OnScrollListener 内部有3个常量来记录ListView的滚动状态

int SCROLL_STATE_FLING                                       The user had previously been scrolling using touch and had performed a fling. 
int SCROLL_STATE_IDLE                                          The view is not scrolling. 
int SCROLL_STATE_TOUCH_SCROLL                  The user is scrolling using touch, and their finger is still on the screen  

知道这些常量代表的含义，我们就可以很轻松的实现 滚动翻页的效果了。

footer_more.xml

 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent"
     android:gravity="center_horizontal"
     android:orientation="horizontal"
     android:padding="15dp" >

     <ProgressBar
         android:id="@+id/pb_load_progress"
         style="@android:style/Widget.ProgressBar.Small.Inverse"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:gravity="center"
         android:indeterminate="true">
     </ProgressBar>

     <TextView
         android:id="@+id/tv_load_more"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginLeft="10.0dp"
         android:gravity="center"
         android:text="@string/load_more_data"
         android:textColor="@color/black" >
     </TextView>

 </LinearLayout>

activity_main.xml

 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     tools:context=".MainActivity" >

     <TextView
         android:id="@+id/tv_title"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_centerHorizontal="true"
         android:layout_marginTop="5dp"
         android:text="@string/load_more"
         android:textSize="15sp" />

     <ListView
         android:id="@+id/mListView"
         android:layout_below="@id/tv_title"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:cacheColorHint="@android:color/transparent" />

 </RelativeLayout>

list_item.xml

 <?xml version="1.0" encoding="utf-8"?>
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content" >

     <ImageView
         android:id="@+id/iv_icon"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:contentDescription="@string/app_name"
         android:src="@drawable/ic_launcher" />

     <TextView
         android:id="@+id/tv_title"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_toRightOf="@id/iv_icon"
         android:textSize="18sp"
         android:textColor="@color/black"/>

     <TextView
         android:id="@+id/tv_content"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_toRightOf="@id/iv_icon"
         android:layout_below="@id/tv_title"
         android:layout_marginTop="5dp"
         android:textSize="15sp"
         android:textColor="@color/black"/>

 </RelativeLayout>

 package com.example.loadmore;

 import java.util.ArrayList;
 import java.util.List;

 import com.example.loadmore.entity.DataNews;

 import android.app.Activity;
 import android.content.Context;
 import android.os.Bundle;
 import android.os.Handler;
 import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.AbsListView;
 import android.widget.AbsListView.OnScrollListener;
 import android.widget.BaseAdapter;
 import android.widget.ListView;
 import android.widget.ProgressBar;
 import android.widget.TextView;

 public class MainActivity extends Activity implements OnScrollListener {

     private static final int LOAD_DATA_FINISH = 1;

     private static final String TAG = MainActivity.class.getName();

     private List<DataNews> dataList = new ArrayList<DataNews>();
     private Handler handler = new Handler() {
         public void handleMessage(android.os.Message msg) {
             switch (msg.what) {
             case LOAD_DATA_FINISH:
                 tv_load_more.setText(R.string.load_more_data);
                 pb_load_progress.setVisibility(View.GONE);

                 if(mAdapter!=null){
                     mAdapter.notifyDataSetChanged();
                 }

                 break;

             default:
                 break;
             }
         };
     };

     private int startIndex = 0;
     private int requestSize = 10;

     private ListView mListView;

     private View moreView;

     private DataAdapter mAdapter;

     private int lastItem;

     private TextView tv_load_more;

     private ProgressBar pb_load_progress;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         findView();
         setListener();
     }

     private void findView() {
         LayoutInflater inflater = LayoutInflater.from(getApplicationContext());

         moreView = inflater.inflate(R.layout.footer_more, null);

         tv_load_more = (TextView) moreView.findViewById(R.id.tv_load_more);
         pb_load_progress = (ProgressBar) moreView.findViewById(R.id.pb_load_progress);

         mListView = (ListView) findViewById(R.id.mListView);

         for (int i = 0; i < 10; i++) {
             DataNews dn = new DataNews();
             dn.setTitle("第 " + i + " 行标题");
             dn.setContent("" + i + " 行内容");

             dataList.add(dn);
         }
         mListView.addFooterView(moreView);
         mAdapter = new DataAdapter(getApplicationContext());
         mListView.setAdapter(mAdapter);
     }

     private void setListener() {
         mListView.setOnScrollListener(this);
     }

     @Override
     public void onScroll(AbsListView view, int firstVisibleItem,
             int visibleItemCount, int totalItemCount) {

         lastItem = firstVisibleItem + visibleItemCount - 1;

         // Log.i(TAG,
         // "firstVisibleItem:"+firstVisibleItem+"visibleItemCount:"+visibleItemCount+" lastItem:"+lastItem);
     }

     @Override
     public void onScrollStateChanged(AbsListView view, int scrollState) {

         if (lastItem == mAdapter.getCount()
                 && scrollState == OnScrollListener.SCROLL_STATE_IDLE) {

             Log.e(TAG, "load more");

             startIndex += requestSize;

             loadMoreData();
         }
     }

     private void loadMoreData() {

         tv_load_more.setText(R.string.loading_data);
         pb_load_progress.setVisibility(View.VISIBLE);

         new Thread(){

             public void run() {

                 if (startIndex + requestSize <50) {

                     for (int i = startIndex; i < startIndex + requestSize; i++) {

                         DataNews dn = new DataNews();
                         dn.setTitle("增加 第 " + i + " 行标题");
                         dn.setContent("增加 第 " + i + " 行内容");

                         dataList.add(dn);
                     }

                     try {
                         Thread.sleep(3000);
                     } catch (InterruptedException e) {
                         e.printStackTrace();
                     }

                     handler.sendEmptyMessage(LOAD_DATA_FINISH);

                 }else{
                     handler.postDelayed(new Runnable() {

                         @Override
                         public void run() {

                             tv_load_more.setText(R.string.no_more_data);
                             pb_load_progress.setVisibility(View.GONE);

                         }
                     }, 1000);
                 }

             };
         }.start();
     }

     private class DataAdapter extends BaseAdapter {
         private Context ctx;
         private LayoutInflater inflater;

         public DataAdapter(Context ctx) {
             this.ctx = ctx;
             inflater = LayoutInflater.from(ctx);
         }

         @Override
         public int getCount() {

             return dataList == null ? 0 : dataList.size();
         }

         @Override
         public Object getItem(int position) {
             // TODO Auto-generated method stub
             return dataList.get(position);
         }

         @Override
         public long getItemId(int position) {
             // TODO Auto-generated method stub
             return position;
         }

         @Override
         public View getView(int position, View convertView, ViewGroup parent) {
             ViewHolder holder;
             if (convertView == null) {
                 convertView = inflater.inflate(R.layout.list_item, null);

                 holder = new ViewHolder();
                 holder.tv_title = (TextView) convertView
                         .findViewById(R.id.tv_title);
                 holder.tv_content = (TextView) convertView
                         .findViewById(R.id.tv_content);

                 convertView.setTag(holder);
             } else {
                 holder = (ViewHolder) convertView.getTag();
             }

             DataNews dn = dataList.get(position);

             holder.tv_title.setText(dn.getTitle());
             holder.tv_content.setText(dn.getContent());

             return convertView;
         }
     }

     static class ViewHolder {
         public TextView tv_title;
         public TextView tv_content;
     }

 }

运行效果截图

正常状态时

滚动到底部时

没有更多数据时