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Android项目开发全程（四）-- 将网络返回的json字符串轻松转换成listview列表

前面几篇博文介绍了从项目搭建到获取网络字符串，对一个项目的前期整体工作进行了详细的介绍，本篇接着上篇介绍一下怎么样优雅将网络返回的json字符串轻松转换成listview列表。

先上图，看一下效果。

包括下拉刷新和上拉加载更多两个功能，怎样还算可以吧~，比起前几篇博文中的那一大片一大片的“乱码”看起来是不是舒服多了。

一、对界面面布局

1、Android默认的标题栏不太好看，咱们需要换成自己的。在AndroidManifest.xml文件中将APP主题设为NoTitleBar

1 <application 2         android:allowBackup="true" 3         android:icon="@drawable/ic_launcher" 4         android:label="@string/app_name" 5         android:theme="@android:style/Theme.NoTitleBar" > 6 </application>

2、然后在每个局部文件中加上自己创建的标题，为了以后便于管理，最好将标题作为一个单独的布局文件（title_layout.xml），然后通过include引用。

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  2     xmlns:tools="http://schemas.android.com/tools"  3     android:layout_width="match_parent"  4     android:layout_height="44dp"  5     android:orientation="horizontal" >  6     <TextView  7         android:id="@+id/app_title"  8         android:layout_width="fill_parent"  9         android:layout_height="44dp" 10         android:gravity="center" 11         android:background="#FFA500" 12         android:textColor="#FFF" 13         android:textSize="20dp" 14         android:text="@string/app_name" /> 15 </LinearLayout>

3、创建主界面（activity_main.xml）

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  2     xmlns:tools="http://schemas.android.com/tools"  3     android:layout_width="match_parent"  4     android:layout_height="match_parent"  5     android:background="#ededed"  6     android:orientation="vertical" >  7     <!--引用标题栏-->  8     <include layout="@layout/title_layout"/>  9     <!-- 第三方类库的listview，可下拉刷新，上拉加载更多 --> 10     <com.handmark.pulltorefresh.library.PullToRefreshListView 11         android:id="@+id/pull_refresh_list" 12         android:layout_width="fill_parent" 13         android:layout_height="fill_parent" 14         android:layout_weight="1.0" 15         android:layout_marginTop="3dp" 16         android:cacheColorHint="#00000000" 17         android:divider="@null" 18         android:fadingEdge="none" 19         android:fastScrollEnabled="false" 20         android:footerDividersEnabled="false" 21         android:headerDividersEnabled="false" 22         android:scrollbars="none" 23         android:smoothScrollbar="true"/> 24 </LinearLayout>

这里通过include引用了title_layout.xml文件，listview控件使用的第三方类库PullToRefresh，下载时会一并给出。

4、创建listview的item布局（item_main.xml）

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  2     xmlns:tools="http://schemas.android.com/tools"  3     android:layout_width="match_parent"  4     android:layout_height="wrap_content"  5     android:paddingTop="3dp"  6     android:paddingBottom="3dp"  7     android:paddingLeft="8dp"  8     android:paddingRight="8dp"  9     android:orientation="vertical" > 10      11     <LinearLayout  12         android:layout_width="match_parent" 13         android:layout_height="wrap_content" 14         android:padding="10dp" 15         android:background="@drawable/bg_shape" 16         android:orientation="vertical" > 17  18         <TextView 19             android:id="@+id/tv_title" 20             android:layout_width="fill_parent" 21             android:layout_height="wrap_content" 22             android:singleLine="true" 23             android:textColor="#3b3d42" 24             android:textSize="16dp" /> 25  26         <TextView 27             android:id="@+id/tv_time" 28             android:layout_width="fill_parent" 29             android:layout_height="wrap_content" 30             android:layout_marginTop="3dp" 31             android:textColor="#636251" 32             android:textSize="12dp" /> 33         <TextView 34             android:id="@+id/tv_content" 35             android:layout_width="fill_parent" 36             android:layout_height="wrap_content" 37             android:textColor="#636251" 38             android:textSize="16dp" 39             android:layout_marginTop="8dp" /> 40     </LinearLayout> 41 </LinearLayout>

二、创建Adapter（MainAdapter.java）

 1 public class MainAdapter extends BaseAdapter {  2     private Context context;  3     private List<Map<String, Object>> list;  4     private LayoutInflater inflater;  5     public MainAdapter(Context context, List<Map<String, Object>> list) {  6         this.context = context;  7         inflater = inflater.from(context);  8         this.list = list;  9     } 10     @Override 11     public int getCount() { 12         // TODO Auto-generated method stub 13         return list.size(); 14     } 15  16     @Override 17     public Object getItem(int arg0) { 18         // TODO Auto-generated method stub 19         return list.get(arg0); 20     } 21  22     @Override 23     public long getItemId(int arg0) { 24         // TODO Auto-generated method stub 25         return arg0; 26     } 27  28     @Override 29     public View getView(int position, View convertView, ViewGroup parent) { 30         // TODO Auto-generated method stub 31         Holder holder = null; 32         Map<String, Object> map = list.get(position); 33         if(holder == null){ 34             holder = new Holder(); 35             convertView = inflater.inflate(R.layout.item_main, null); 36             holder.title = (TextView) convertView.findViewById(R.id.tv_title); 37             holder.time = (TextView) convertView.findViewById(R.id.tv_time); 38             holder.content = (TextView) convertView.findViewById(R.id.tv_content); 39             convertView.setTag(holder); 40         } 41         holder.title.setText(map.get("title").toString()); 42         holder.time.setText(map.get("publishDate").toString()); 43         holder.content.setText(map.get("content").toString()); 44         return convertView; 45     } 46      47     class Holder { 48         public TextView title; 49         public TextView time; 50         public TextView content; 51     } 52 }

这里的MainAdapter继承了BaseAdapter，为listview提供适配器。

三、在MainActivity操作数据（分步讲解）

1、初始化pullRefreshList（是一个PullToRefreshListView，第三方类库PullToRefresh，可上拉刷新，下拉加载更多）

 1 //初始化pullRefreshList  2     public void initListView(){  3         pullRefreshList.setMode(Mode.BOTH);  4         layoutProxy = pullRefreshList.getLoadingLayoutProxy(true, false);  5         layoutProxy.setPullLabel("下拉刷新");  6         layoutProxy.setReleaseLabel("松开立即刷新");  7         layoutProxy.setRefreshingLabel("正在载入");  8         layoutProxybottom = pullRefreshList.getLoadingLayoutProxy(false, true);  9         layoutProxybottom.setPullLabel("上拉加载更多"); 10         layoutProxybottom.setReleaseLabel("松开立即刷新"); 11         layoutProxybottom.setRefreshingLabel("正在载入"); 12         pullRefreshList.setOnRefreshListener(new MyRefresh()); 13         listView = pullRefreshList.getRefreshableView(); 14         lists = new ArrayList<Map<String,Object>>(); 15         adapter = new MainAdapter(getApplicationContext(), lists); 16         listView.setAdapter(adapter); 17     }

2、设置pullRefreshList的刷新监听器，当上拉是表示刷新，将参数page设为第一页，提交请求。当下拉时表示加载更多，将page+1，然后提交请求。

 1 class MyRefresh implements OnRefreshListener2<ListView>{  2     //上拉是回调此方法  3         @Override  4         public void onPullDownToRefresh(PullToRefreshBase<ListView> refreshView) {  5             page = 1;  6             getNetData.getLaughBy360(REQUEST_360LAUGH_CODE, page + "");  7         }  8     //下拉时回调此方法  9         @Override 10         public void onPullUpToRefresh(PullToRefreshBase<ListView> refreshView) { 11             if(page < 34){  //目前接口中一个有34页数据 12                 page += 1; 13                 getNetData.getLaughBy360(REQUEST_360LAUGH_CODE, page + ""); 14                 mHandler.sendEmptyMessage(DIALOG_SHOW); 15             } else { 16                 pullRefreshList.onRefreshComplete(); 17                 Toast.makeText(getApplicationContext(), "已经是最后一页了", Toast.LENGTH_SHORT).show(); 18             } 19         } 20     }

3、在网络请求的回调方法中，利用jackson工具的ObjectMapper可以很容易的将json字符串转换成Map（也可根据需要转换成List、对象等等）

 1 public void onCallBackSuccessed(int notify, String result) {  2         if(notify == REQUEST_360LAUGH_CODE){  3             try {  4                 //使用Jackson工具的ObjectMapper直接将json字符串转换成Map格式  5                 Map<String, Object> map = objectMapper.readValue(result, Map.class);  6                 List<Map<String, Object>> list = (List<Map<String, Object>>) map.get("jokes");  7                 if(page == 1) {  8                     lists.clear();  9                 } 10                 if(list.size() == 0){ 11                     Toast.makeText(getApplicationContext(), "木有笑话了", Toast.LENGTH_SHORT).show(); 12                 } else { 13                     lists.addAll(list); 14                     //改变adapter数据 15                     adapter.notifyDataSetChanged(); 16                 } 17             } catch (JsonParseException e) { 18                 // TODO Auto-generated catch block 19                 e.printStackTrace(); 20             } catch (JsonMappingException e) { 21                 // TODO Auto-generated catch block 22                 e.printStackTrace(); 23             } catch (IOException e) { 24                 // TODO Auto-generated catch block 25                 e.printStackTrace(); 26             } 27         } 28         mHandler.sendEmptyMessage(DIALOG_CONCEL); 29         pullRefreshList.onRefreshComplete(); 30     }

分析一下，这里每次从网络上获取的结果转成后都先加入到一个临时的list中，当page=1时，说明此事是上拉刷新或者首次请求。这时候将直接将lists清空来接受最新数据，当page !=1 时说明是加载更多的请求，无需清空lists，如果新返回的数据不为空则将list加入到lists中，然后通知adapter数据改变。

别忘了设置onRefreshComplete完成刷新状态。

最后，整个的MainActivity.java如下：

  1 package com.laughdemo.main;   2 import java.io.IOException;   3 import java.util.ArrayList;   4 import java.util.List;   5 import java.util.Map;   6 import net.tsz.afinal.annotation.view.ViewInject;   7 import org.codehaus.jackson.JsonParseException;   8 import org.codehaus.jackson.map.JsonMappingException;   9 import android.os.Bundle;  10 import android.widget.ListView;  11 import android.widget.Toast;  12 import com.handmark.pulltorefresh.library.ILoadingLayout;  13 import com.handmark.pulltorefresh.library.PullToRefreshBase;  14 import com.handmark.pulltorefresh.library.PullToRefreshBase.Mode;  15 import com.handmark.pulltorefresh.library.PullToRefreshBase.OnRefreshListener2;  16 import com.handmark.pulltorefresh.library.PullToRefreshListView;  17 import com.laughdemo.adapter.MainAdapter;  18 import com.laughdemo.http.DataCallBack;  19 import com.laughdemo.http.GetNetData;  20 import com.laughdemo.utils.Constants;  21 /**  22  * 主窗体类  23  * @author 刘伟    2015.7.3  24  *  25  */  26 public class MainActivity extends BaseActivity implements Constants, DataCallBack{  27     final String TAG = "MainActivity";  28     GetNetData getNetData;  29     MainAdapter adapter;  30     private int page = 1;  31     ListView listView;  32     List<Map<String, Object>> lists;  33     private ILoadingLayout layoutProxy;  34     private ILoadingLayout layoutProxybottom;  35     @ViewInject(id=R.id.pull_refresh_list) PullToRefreshListView pullRefreshList;  36     @Override  37     protected void onCreate(Bundle savedInstanceState) {  38         super.onCreate(savedInstanceState);  39         setContentView(R.layout.activity_main);  40         initListView();  41         getNetData = new GetNetData(this);  42         getNetData.getLaughBy360(REQUEST_360LAUGH_CODE, page + "");  43         mHandler.sendEmptyMessage(DIALOG_SHOW);  44     }  45       46     //初始化pullRefreshList  47     public void initListView(){  48         pullRefreshList.setMode(Mode.BOTH);  49         layoutProxy = pullRefreshList.getLoadingLayoutProxy(true, false);  50         layoutProxy.setPullLabel("下拉刷新");  51         layoutProxy.setReleaseLabel("松开立即刷新");  52         layoutProxy.setRefreshingLabel("正在载入");  53         layoutProxybottom = pullRefreshList.getLoadingLayoutProxy(false, true);  54         layoutProxybottom.setPullLabel("上拉加载更多");  55         layoutProxybottom.setReleaseLabel("松开立即刷新");  56         layoutProxybottom.setRefreshingLabel("正在载入");  57         pullRefreshList.setOnRefreshListener(new MyRefresh());  58         listView = pullRefreshList.getRefreshableView();  59         lists = new ArrayList<Map<String,Object>>();  60         adapter = new MainAdapter(getApplicationContext(), lists);  61         listView.setAdapter(adapter);  62     }  63       64     class MyRefresh implements OnRefreshListener2<ListView>{  65   66         @Override  67         public void onPullDownToRefresh(PullToRefreshBase<ListView> refreshView) {  68             page = 1;  69             getNetData.getLaughBy360(REQUEST_360LAUGH_CODE, page + "");  70         }  71   72         @Override  73         public void onPullUpToRefresh(PullToRefreshBase<ListView> refreshView) {  74             if(page < 34){  75                 page += 1;  76                 getNetData.getLaughBy360(REQUEST_360LAUGH_CODE, page + "");  77                 mHandler.sendEmptyMessage(DIALOG_SHOW);  78             } else {  79                 pullRefreshList.onRefreshComplete();  80                 Toast.makeText(getApplicationContext(), "已经是最后一页了", Toast.LENGTH_SHORT).show();  81             }  82         }  83     }  84     @Override  85     public void onCallBackSuccessed(int notify, String result) {  86         if(notify == REQUEST_360LAUGH_CODE){  87             try {  88                 //使用Jackson工具的ObjectMapper直接将json字符串转换成Map格式  89                 Map<String, Object> map = objectMapper.readValue(result, Map.class);  90                 List<Map<String, Object>> list = (List<Map<String, Object>>) map.get("jokes");  91                 if(page == 1) {  92                     lists.clear();  93                 }  94                 if(list.size() == 0){  95                     Toast.makeText(getApplicationContext(), "木有笑话了", Toast.LENGTH_SHORT).show();  96                 } else {  97                     lists.addAll(list);  98                     //改变adapter数据  99                     adapter.notifyDataSetChanged(); 100                 } 101             } catch (JsonParseException e) { 102                 // TODO Auto-generated catch block 103                 e.printStackTrace(); 104             } catch (JsonMappingException e) { 105                 // TODO Auto-generated catch block 106                 e.printStackTrace(); 107             } catch (IOException e) { 108                 // TODO Auto-generated catch block 109                 e.printStackTrace(); 110             } 111         } 112         mHandler.sendEmptyMessage(DIALOG_CONCEL); 113         pullRefreshList.onRefreshComplete(); 114     } 115     @Override 116     public void onCallBackFailed(int notify) { 117         mHandler.sendEmptyMessage(DIALOG_CONCEL); 118         pullRefreshList.onRefreshComplete(); 119         Toast.makeText(getApplicationContext(), "网络连接失败", Toast.LENGTH_LONG).show(); 120     } 121 }