如何绑定的ListView对象中的片段？ [英] How to bind ListView Objects in Fragments?
问题描述
我有一个问题，我的JSON数据对象绑定到ListView片段。我发现了一个NPE在第100行，我绑定到我的简单的适配器。我试图了解这样做的各种方法，但都没有成功。据<一href="http://developer.android.com/reference/android/app/ListFragment.html#setListAdapter%28android.widget.ListAdapter%29"相对=nofollow>的文档：
您必须使用<一个href="http://developer.android.com/reference/android/app/ListFragment.html#setListAdapter%28android.widget.ListAdapter%29"相对=nofollow> ListFragment.setListAdapter（）到列表中与关联 的适配器。不要直接调用ListView.setAdapter（），否则 重要的初始化将被跳过。
我敢肯定，这是我的问题，但我不知道如何去纠正我的code。下面是NPE和我的活动。请任何帮助将AP preciated，尤其是因为我学习，我去....一些code例如
主题ID = 1：螺纹未捕获异常退出（组= 0x40a781f8） 致命异常：在主显示java.lang.NullPointerException android.widget.SimpleAdapter（SimpleAdapter.java:85）在 com.andaero.app.NavigationListFragment $ 1.callback（NavigationListFragment.java:100） 在 com.andaero.app.NavigationListFragment $ 1.callback（NavigationListFragment.java:1） 在 com.androidquery.callback.AbstractAjaxCallback.callback（AbstractAjaxCallback.java:440） 在 com.androidquery.callback.AbstractAjaxCallback.afterWork（AbstractAjaxCallback.java:1010） 在 com.androidquery.callback.AbstractAjaxCallback.run（AbstractAjaxCallback.java:804） 在android.os.Handler.handleCallback（Handler.java:605）在 android.os.Handler.dispatchMessage（Handler.java:92）在 android.os.Looper.loop（Looper.java:137）在 android.app.ActivityThread.main（ActivityThread.java:4424）在 java.lang.reflect.Method.invokeNative（本机方法）在 java.lang.reflect.Method.invoke（Method.java:511）在 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:787） 在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:554）在 dalvik.system.NativeStart.main（本机方法）
公共类NavigationListFragment扩展ListFragment {
上下文语境;
私人活动℃;
最后AQuery AQ =新AQuery（C）;
私有静态字符串URL =http://192.168.1.17/Andaero/php/regulatory_list.php;
@覆盖
公共查看onCreateView（LayoutInflater充气，容器的ViewGroup，捆绑savedInstanceState）{
最终的视图中查看= inflater.inflate（R.layout.listview，集装箱，假）;
Log.i（NavigationListFragment，ListView的充气!!）;
返回查看;
}
@覆盖
公共无效onActivityCreated（包savedInstanceState）{
super.onActivityCreated（savedInstanceState）;
// AsyncTasks.getJSONArrays（上下文）;用于获取//异步任务
// JSONarray
aq.ajax（URL，JSONArray.class，新AjaxCallback＆LT; JSONArray＆GT;（）{
// JSON节点名称
私有静态最后弦乐TAG_ID =_id;
私有静态最后弦乐TAG_LABEL =标签;
私有静态最后弦乐TAG_TITLE =称号;
私有静态最后弦乐TAG_DISCR =说明;
私有静态最后弦乐TAG_GO2URL =gotoURL;
公共无效回调（字符串URL，JSONArray JSON，AjaxStatus状态）{
如果（JSON！= NULL）{
// NavigationListFragment.jsonListCallback（JSON）;
Log.i（NavigationListFragment，陷入JSON：+ json.toString（））;
//哈希映射为的ListView
ArrayList的＆LT; HashMap的＆LT;字符串，字符串＆GT;＆GT; mList =新的ArrayList＆LT; HashMap的＆LT;字符串，字符串＆GT;＆GT;（）;
尝试 {
//解析字符串到JSON对象
的for（int i = 0; I＆LT; json.length（）;我++）{
的JSONObject json_data = json.getJSONObject（ⅰ）;
//保存在变量中的每个JSON项目
字符串ID = json_data.getString（TAG_ID）;
字符串标签= json_data.getString（TAG_LABEL）;
字符串标题= json_data.getString（TAG_TITLE）;
字符串描述= json_data.getString（TAG_DISCR）;
字符串gotoURL = json_data.getString（TAG_GO2URL）;
//创建新的HashMap
HashMap的＆LT;字符串，字符串＆GT;图=新的HashMap＆LT;字符串，字符串＆GT;（）;
//添加每个子节点HashMap中的key =＆GT;值
map.put（tag_id，分别编号）;
map.put（TAG_LABEL，标签）;
map.put（TAG_TITLE，职称）;
map.put（TAG_DISCR，说明）;
map.put（TAG_GO2URL，gotoURL）;
//添加HashList到ArrayList中
mList.add（图）
Log.i（NavigationListFragment，散列：+地图）;
}
}赶上（JSONException E）{
Log.e（log_tag，错误分析数据+ e.toString（））;
}
//创建列表项映射
字符串从=新的String [] {TAG_LABEL，TAG_TITLE，TAG_DISCR，TAG_GO2URL} [];
INT []到=新INT [] {R.id.listLabel，R.id.listTitle，R.id.listDiscription，R.id.dummy};
//更新已解析JSON数据到ListView控件
SimpleAdapter适配器=新SimpleAdapter（C，mList，R.layout.list_item，从，到）; //＆LT; - NPE IS HERE
setListAdapter（适配器）;
//选择单一的ListView项
ListView的LV = getListView（）;
//启动新的页面中选择单列表项
lv.setOnItemClickListener（新OnItemClickListener（）{
公共无效onItemClick（适配器视图＆LT;＆GT;母公司视图中查看，
INT位置，长的id）{
//去做
}
}）;
}
//登录任何网络/ JSON错误
开关（status.get code（））{
案例AjaxStatus.TRANSFORM_ERROR：
Log.i（GetJSONArray，TRANSFORM_ERROR）;
打破;
案例AjaxStatus.NETWORK_ERROR：
Log.i（GetJSONArray，NETWORK_ERROR）;
// TODO创建警报对话框
案例AjaxStatus.AUTH_ERROR：
Log.i（GetJSONArray，AUTH_ERROR）;
打破;
}
}
}）;
}
}
除非你是忽略code你永远不分配的 C值或上下文。
在调用
SimpleAdapter适配器=新SimpleAdapter（C，mList，R.layout.list_item，从，到）;
正在传递C，这将永远是空的。
开关C到 getActivity（），问题应该消失
Additionaly，
最后AQuery AQ =新AQuery（C）;
您应该初始化这个一旦你知道你有机会到getActivity（）。当创建一个片段也不会立即访问的活动，直到连接（..）被调用。
I am having an issue binding my JSON data Object to a listView fragment. I'm getting an NPE at line 100 where I bind to my Simple Adapter. I have tried various ways about doing this but have been unsuccessful. According to the docs:
You must use ListFragment.setListAdapter() to associate the list with an adapter. Do not directly call ListView.setAdapter() or else important initialization will be skipped.
I'm sure that is my issue but I don't know how to go about correcting my code. Below is the NPE and my activity. Please any help will be appreciated, esp some code example because I'm learning as I go....
threadid=1: thread exiting with uncaught exception (group=0x40a781f8) FATAL EXCEPTION: main java.lang.NullPointerException at android.widget.SimpleAdapter.(SimpleAdapter.java:85) at com.andaero.app.NavigationListFragment$1.callback(NavigationListFragment.java:100) at com.andaero.app.NavigationListFragment$1.callback(NavigationListFragment.java:1) at com.androidquery.callback.AbstractAjaxCallback.callback(AbstractAjaxCallback.java:440) at com.androidquery.callback.AbstractAjaxCallback.afterWork(AbstractAjaxCallback.java:1010) at com.androidquery.callback.AbstractAjaxCallback.run(AbstractAjaxCallback.java:804) at android.os.Handler.handleCallback(Handler.java:605) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:4424) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554) at dalvik.system.NativeStart.main(Native Method)
public class NavigationListFragment extends ListFragment {
Context context;
private Activity c;
final AQuery aq = new AQuery(c);
private static String url = "http://192.168.1.17/Andaero/php/regulatory_list.php";
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
final View view = inflater.inflate(R.layout.listview, container, false);
Log.i("NavigationListFragment", "ListView Inflated!!");
return view;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
// AsyncTasks.getJSONArrays(context);// asynchronous task for getting
// JSONarray
aq.ajax(url, JSONArray.class, new AjaxCallback<JSONArray>() {
// JSON Node names
private static final String TAG_ID = "_id";
private static final String TAG_LABEL = "label";
private static final String TAG_TITLE = "title";
private static final String TAG_DISCR = "description";
private static final String TAG_GO2URL = "gotoURL";
public void callback(String url, JSONArray json, AjaxStatus status) {
if (json != null) {
// NavigationListFragment.jsonListCallback(json);
Log.i("NavigationListFragment", "Caught JSON: " + json.toString());
// Hashmap for ListView
ArrayList<HashMap<String, String>> mList = new ArrayList<HashMap<String, String>>();
try {
// Parse the string to a JSON object
for (int i = 0; i < json.length(); i++) {
JSONObject json_data = json.getJSONObject(i);
// Storing each json item in variable
String id = json_data.getString(TAG_ID);
String label = json_data.getString(TAG_LABEL);
String title = json_data.getString(TAG_TITLE);
String description = json_data.getString(TAG_DISCR);
String gotoURL = json_data.getString(TAG_GO2URL);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, id);
map.put(TAG_LABEL, label);
map.put(TAG_TITLE, title);
map.put(TAG_DISCR, description);
map.put(TAG_GO2URL, gotoURL);
// adding HashList to ArrayList
mList.add(map);
Log.i("NavigationListFragment", "Hash: " + map);
}
} catch (JSONException e) {
Log.e("log_tag", "Error parsing data " + e.toString());
}
// create the list item mapping
String[] from = new String[] {TAG_LABEL, TAG_TITLE, TAG_DISCR, TAG_GO2URL};
int[] to = new int[] { R.id.listLabel, R.id.listTitle, R.id.listDiscription, R.id.dummy };
// Updating parsed JSON data into ListView
SimpleAdapter adapter = new SimpleAdapter(c, mList, R.layout.list_item, from, to);//<--NPE IS HERE
setListAdapter(adapter);
// selecting single ListView item
ListView lv = getListView();
// Launching new screen on Selecting Single ListItem
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
//TODO
}
});
}
// Log any network/JSON Errors
switch (status.getCode()) {
case AjaxStatus.TRANSFORM_ERROR :
Log.i("GetJSONArray", "TRANSFORM_ERROR");
break;
case AjaxStatus.NETWORK_ERROR :
Log.i("GetJSONArray", "NETWORK_ERROR");
// TODO Create Alert Dialog
case AjaxStatus.AUTH_ERROR :
Log.i("GetJSONArray", "AUTH_ERROR");
break;
}
}
});
}
}
Unless you are omitting code you never assign the value of c or context.
When calling
SimpleAdapter adapter = new SimpleAdapter(c, mList, R.layout.list_item, from, to);
You are passing in "c" which will always be null.
switch "c" to getActivity() and the problem should go away
Additionaly,
final AQuery aq = new AQuery(c);
You should initialize this once you know you have access to getActivity(). When a fragment is created it will not immediately have access to the activity until attach(..) is called.
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