ListView分页

和大多数初级玩家一样，偶也终于玩到分页了~ ~分页有两个方法：一个是handler,一个是AsyncTask.

我的listview里没有包括图像，所以就没有用到AsyncTask.

准备工作：1.一个用来显示正在加载的xml文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/loading_layout"
    android:layout_width="fill_parent"
     android:layout_height="fill_parent"
    android:orientation="vertical"
     android:gravity="center_horizontal"
    >
    <RelativeLayout
        android:id="@+id/load_id"
        android:orientation="horizontal" 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        >
        
        <TextView 
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:gravity="center_vertical"
            android:text="Loading..."
            android:textSize="12pt" />
        
        <ProgressBar android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="center_vertical"
            android:layout_alignParentRight="true"/>
    </RelativeLayout>
</LinearLayout>

2.listview布局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/customer_list"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="#ffffff"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/lv_newtask"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="5dip"
        android:layout_marginRight="5dip"
        android:cacheColorHint="#ffffff"
        android:divider="#ffffff"
        android:dividerHeight="5dip"
        android:listSelector="#00000000" >
    </ListView>
</LinearLayout>

3.listview_item

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:background="@drawable/newtask_selector_bg"
    android:minHeight="?android:attr/listPreferredItemHeight" >

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_toLeftOf="@+id/avatar_image"
        android:orientation="vertical" >

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal" >

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:paddingLeft="5dip"
                android:text="订单号:"
                android:textColor="#2894ff"
                android:textSize="17sp" >
            </TextView>

            <TextView
                android:id="@+id/tv_newtask_item_cwb"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:paddingLeft="5dip"
                android:text="01056895426"
                android:textColor="#2894ff"
                android:textSize="17sp" >
            </TextView>
        </LinearLayout>

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal" >

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:paddingLeft="5dip"
                android:text="客户名:"
                android:textColor="#2894ff"
                android:textSize="17sp" >
            </TextView>

            <TextView
                android:id="@+id/tv_newtask_item_consigneeName"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:paddingLeft="5dip"
                android:text="大胡子李"
                android:textColor="#2894ff"
                android:textSize="17sp" >
            </TextView>
        </LinearLayout>

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal" >

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:paddingLeft="5dip"
                android:text="地    址:"
                android:textColor="#2894ff"
                android:textSize="17sp" >
            </TextView>

            <TextView
                android:id="@+id/tv_newtask_item_consigneeAddress"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:paddingLeft="5dip"
                android:text="龙口西"
                android:textColor="#2894ff"
                android:textSize="17sp" >
            </TextView>
        </LinearLayout>

        <TextView
            android:id="@+id/user_status"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:visibility="gone" />

        <TextView
            android:id="@+id/user_id"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:visibility="gone" />
    </LinearLayout>

    <ImageView
        android:id="@+id/iv_newtask_detail"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:background="@drawable/detail" />

</RelativeLayout>

下面就要开始写我们的分页类了。

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.newtask);
        context = this;
        findViews();
        initListView();
    }

TextView tv_newtask_num;
    ListView   lv_newtask;
    Context context;
    View loadingView;
    protected void findViews(){
        tv_newtask_num = (TextView) findViewById(R.id.tv_newtask_num);
        lv_newtask = (ListView) findViewById(R.id.lv_newtask);
        tv_newtask_num.setText(Constant.loginInfo.newTasksCount);
        loadingView = LayoutInflater.from(this).inflate(
                R.layout.list_page_load, null);
    }

初始化listView，第一页

NewTaskAdapter adapter;
    protected void initListView(){
        lv_newtask.addFooterView(loadingView);
        Constant.currentData = getData(currentPage, pageSize);
        adapter = new NewTaskAdapter();
        lv_newtask.setAdapter(adapter);
        lv_newtask.setOnScrollListener(this);
        lv_newtask.setOnItemClickListener(this);
    }

别急，NewTaskAdapter是它的内部类：

class NewTaskAdapter extends BaseAdapter {
        public NewTaskAdapter(){
            DebugLog.i("调用了adapter的构造函数");
        }
         LayoutInflater inflater = LayoutInflater.from(context);
        int count=Constant.currentData.size();
         @Override
        public int getCount() {
            return count;
        }
        @Override
        public TaskInfo getItem(int position) {
            return Constant.currentData.get(position);
        }
        @Override
        public long getItemId(int position) {
            return position;
        }
        @Override
        public View getView(final int position, View convertView, ViewGroup parent) {
            ViewHolder mHolder = null;
            if (convertView == null) {
                mHolder = new ViewHolder();
                convertView = inflater.inflate(R.layout.item_newtask, null);
                mHolder.tv_cwb = (TextView) convertView.findViewById(R.id.tv_newtask_item_cwb);
                mHolder.tv_consigneeName = (TextView) convertView.findViewById(R.id.tv_newtask_item_consigneeName);
                mHolder.tv_consigneeAddress = (TextView) convertView.findViewById(R.id.tv_newtask_item_consigneeAddress);
                mHolder.iv_newtask_detail = (ImageView)convertView.findViewById(R.id.iv_newtask_detail);
                convertView.setTag(mHolder);
            }else{
                mHolder = (ViewHolder) convertView.getTag();
            }
            mHolder.tv_cwb.setText(Constant.currentData.get(position).cwb);
            mHolder.tv_consigneeName.setText(Constant.currentData.get(position).consigneeName);
            mHolder.tv_consigneeAddress.setText(Constant.currentData.get(position).consigneeAddress);
            
            mHolder.iv_newtask_detail.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    Bundle bundle = new Bundle();
                    bundle.putSerializable("taskDetail", Constant.currentData.get(position));
                    Intent intent = new Intent(context,NewTaskDetailActivity.class);
                    intent.putExtras(bundle);
                    context.startActivity(intent);
                }
            });
            return convertView;
        }
        public  class ViewHolder{
            public TextView tv_cwb;
            public TextView tv_consigneeName;
            public TextView tv_consigneeAddress;
            public ImageView iv_newtask_detail; 
        }
    }

 Constant.currentData是什么呢？是我的全局类变量汇总： public  static ArrayList<TaskInfo> currentData = new ArrayList<TaskInfo>();

获取网络数据：

    private ProgressDialog progressDialog;
    //private ArrayList<TaskInfo> tempList = null;
    private String fail_reason;
    protected ArrayList<TaskInfo> getData(int currentPage, int pageSize){
        ArrayList<TaskInfo> tempList = null;
        final String url = String.format(Constant.URL_NEWTASKLIST, Constant.loginInfo.mSessionId,0,pageSize,(currentPage-1)*pageSize);
        DebugLog.i("url: **"+url);
        String result = HttpClient.INSTANCE.get(url);
        if(result!=null){
            TaskInfoListParser parser = new TaskInfoListParser();
            tempList = parser.parse(result);
            fail_reason = parser.reason;
        }
        return tempList;
    }

HttpClient.INSTANCE.get(url);这个方法：

public enum HttpClient {
    INSTANCE; 
    final int Timeouts = 30 * 1000; // milliseconds
    DefaultHttpClient httpClient = null;
    HttpContext localContext = null;
    HttpResponse response = null;
    HttpPost httpPost = null;
    HttpGet httpGet = null;

    public void initHttpClient() {
        HttpParams myParams = new BasicHttpParams();
        HttpConnectionParams.setConnectionTimeout(myParams, Timeouts);
        HttpConnectionParams.setSoTimeout(myParams, Timeouts);
        httpClient = new DefaultHttpClient(myParams);
        localContext = new BasicHttpContext();
    }

    public String get(String url) {
        if (httpClient == null) {
            initHttpClient();
        }
        httpClient.getParams().setParameter(ClientPNames.COOKIE_POLICY,
                CookiePolicy.RFC_2109);

        httpGet = new HttpGet(url);
        response = null;
        httpGet.setHeader("Accept",
                "application/soap+xml,application/dime,multipart/related,text/*");
        httpGet.setHeader("Content-Type", "text/xml;charset=utf-8");
        try {
            response = httpClient.execute(httpGet, localContext);

            if (response != null) {
                HttpEntity entity = response.getEntity();
                if (entity != null) {
                    return EntityUtils.toString(entity, "utf-8");
                }
            } 
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        return "";
    }
}

接下来是重点：监听事件里面实现了分页；

private int last_item_position;
     boolean isLoading = false;//是否加载过,控制加载次数
    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        last_item_position = firstVisibleItem + visibleItemCount - 1;
        if (last_item_position == totalItemCount - 2){//表示在第九个位置加载
            if(!isLoading){
                new Thread(){
                    public void run() {
                        isLoading = true;
                        updateCurrendData();
                    };
                }.start();
            }
        }
    }

private int addnum = 0;//新增加的项目条数
    protected void updateCurrendData(){
        currentPage++;
        ArrayList<TaskInfo> list = getData(currentPage, pageSize);
        Message msg = new Message();
        if(list==null){
            msg.what = Constant.NODATA;
        }else{
            addnum = list.size();
            for(TaskInfo ti:list){
                Constant.currentData.add(ti);
            }
            msg.what = Constant.FINISH;
        }
        handler.sendMessage(msg);
    }

我的handler：

private  int currentPage = 1;
    private  int pageSize = 10;
    protected Handler handler = new Handler(){
        String tips = null;
    public void handleMessage(Message msg) {
        switch(msg.what){
        case Constant.FINISH:
            adapter.count = (currentPage-1)*pageSize+addnum; 
            adapter.notifyDataSetChanged();
            handler.removeMessages(0);
               isLoading = false;
            break;
        case Constant.NODATA:
            Toast.makeText(context, "没有了", Toast.LENGTH_LONG).show();
            lv_newtask.removeFooterView(loadingView);
            break;
        }
        if(tips!=null){
            Toast.makeText(context, tips, Toast.LENGTH_LONG).show();
        }
    };    
    };

这样就实现了分页。一定要注意的是， 

private  int currentPage = 1;
 private  int pageSize = 10;

这两个变量，一定不能设置成static 。这和activity的生命周期有关系。如果设置成了static ，那么onRestart以后，再请求的数据是空的，就会报出所谓的空指针异常了！