我似乎无法将JSON对象加载到ListView中。当代码到达该行时 list.setAdaptor（..）我得到一个InvocationTargetException。
逐步调试我认为JSON对象初始化非常好。 HashMap已正确填充。我认为问题出在我的ArrayAdaptor上，但我不知道出了什么问题。
我是Android新手，这是我第一次处理Adapters，AsyncTask和JSON。 所以我会非常感谢任何帮助。即使你认为你说的是显而易见的，请不要犹豫，提出你认为我接近错误的方式。
以下是我的子活动的代码，我尝试使用JSONObject填充ListView：
（如果您认为需要代码的任何其他部分请注释。我会立即添加）
public class SearchResultListActivity extends ActionBarActivity implements OnItemClickListener{
// for json
private ProgressDialog progress;
ListView list;
TextView ver;
TextView name;
TextView api;
Button Btngetdata;
ArrayList<HashMap<String, String>> oslist = new ArrayList<HashMap<String, String>>();
//URL to get JSON Array
private static String url = "http://api.learn2crack.com/android/jsonos/";
//JSON Node Names
private static final String TAG_OS = "android";
private static final String TAG_VER = "ver";
private static final String TAG_NAME = "name";
private static final String TAG_API = "api";
JSONArray jsonArray = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search_result_list);
if (savedInstanceState == null) {
//zzz commented for let json run. uncomment when remove json getSupportFragmentManager().beginTransaction().add(R.id.container, new PlaceholderFragment()).commit();
}
new JSONParse().execute();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.search_result_list, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will automatically handle clicks on the Home/Up button, so long as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onItemClick(AdapterView<?> arg0, View textView, int rowNumber, long arg3) {
Intent intent = new Intent(this, PropertyDetailActivity.class);
startActivity(intent);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_search_result_list, container, false);
return rootView;
}
}
// This is the custom adapter class where you will manage the behavior of your ListView content
public class MyArrayAdapter extends ArrayAdapter<String>{
Context context;
int layoutResourceId; // This is the layout you created for the list items
String data[] = null; // the array with the data to populate the listview
public MyArrayAdapter(Context context, int layoutResourceId, String[] data) {
super(context, layoutResourceId, data);
this.layoutResourceId = layoutResourceId;
this.context = context;
this.data = data;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View row = convertView;
LayoutInflater inflater = ((Activity) getContext()).getLayoutInflater();
row = inflater.inflate(layoutResourceId, parent, false);
TextView txtTitle = (TextView)row.findViewById(R.id.listViewSearchResultTxtTitle);
txtTitle.setText(data[position]);
return row;
}
}
//*********************************** inner class
public class JSONParse extends AsyncTask<String, String, JSONObject> {
private ProgressDialog pDialog;
@Override
protected void onPreExecute() {
super.onPreExecute();
ver = (TextView)findViewById(R.id.listViewSearchResultTxtTitle);
name = (TextView)findViewById(R.id.listViewSearchResultTxtBody1);
api = (TextView)findViewById(R.id.listViewSearchResultTxtBody2);
}
@Override
protected JSONObject doInBackground(String... args) {
JSONParser jParser = new JSONParser();
JSONObject json = jParser.getJSONFromUrl(url);
return json;
}
@Override
protected void onPostExecute(JSONObject json) {
//pDialog.dismiss();
Toast.makeText(getApplicationContext(), " 2000 "+json.toString() , Toast.LENGTH_LONG).show();
try {
// Getting JSON Array from URL
jsonArray = json.getJSONArray(TAG_OS);
for(int i = 0; i < jsonArray.length(); i++){
JSONObject c = jsonArray.getJSONObject(i);
// Storing JSON item in a Variable
String ver = c.getString(TAG_VER);
String name = c.getString(TAG_NAME);
String api = c.getString(TAG_API);
//Adding value HashMap key => value
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_VER, ver);
map.put(TAG_NAME, name);
map.put(TAG_API, api);
oslist.add(map);
}
ListAdapter adapter = new SimpleAdapter( getApplicationContext() , oslist, R.layout.list_view_items, new String[] { TAG_VER,TAG_NAME, TAG_API }, new int[] {
//R.id.listViewSearchResultTxtTitle,
R.id.listViewSearchResultTxtBody1, R.id.listViewSearchResultTxtBody2});
list=(ListView)findViewById(R.id.listViewSearchResult);
list.setAdapter(adapter);
}
catch (JSONException e) {
e.printStackTrace();
}
}
public void showProgressDialog(final String msg) {
runOnUiThread(new Runnable() {
public void run() {
if (progress == null || !progress.isShowing()) {
progress = ProgressDialog.show(getApplicationContext(), "", msg);
}
}
});
}
public void hideProgressDialog() {
runOnUiThread(new Runnable() {
@Override
public void run() {
try {
if (progress.isShowing())
progress.dismiss();
}
catch (Throwable e) {
}
}
});
}
}
//json end
}
这是LogCat错误。 （当我调试时，我得到了InvocationTargetException，而LogCat给了我NullPointerException。我现在不知道他们为什么不同：S）
6-03 08:11:56.412: E/AndroidRuntime(5681): FATAL EXCEPTION: main
06-03 08:11:56.412: E/AndroidRuntime(5681): Process: com.****, PID: 5681
06-03 08:11:56.412: E/AndroidRuntime(5681): java.lang.NullPointerException
06-03 08:11:56.412: E/AndroidRuntime(5681): at com...SearchResultListActivity$JSONParse.onPostExecute(SearchResultListActivity.java:162)
06-03 08:11:56.412: E/AndroidRuntime(5681): at com..SearchResultListActivity$JSONParse.onPostExecute(SearchResultListActivity.java:1)
06-03 08:11:56.412: E/AndroidRuntime(5681): at android.os.AsyncTask.finish(AsyncTask.java:632)
06-03 08:11:56.412: E/AndroidRuntime(5681): at android.os.AsyncTask.access$600(AsyncTask.java:177)
06-03 08:11:56.412: E/AndroidRuntime(5681): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
06-03 08:11:56.412: E/AndroidRuntime(5681): at android.os.Handler.dispatchMessage(Handler.java:102)
06-03 08:11:56.412: E/AndroidRuntime(5681): at android.os.Looper.loop(Looper.java:136)
06-03 08:11:56.412: E/AndroidRuntime(5681): at android.app.ActivityThread.main(ActivityThread.java:5017)
06-03 08:11:56.412: E/AndroidRuntime(5681): at java.lang.reflect.Method.invokeNative(Native Method)
06-03 08:11:56.412: E/AndroidRuntime(5681): at java.lang.reflect.Method.invoke(Method.java:515)
06-03 08:11:56.412: E/AndroidRuntime(5681): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
06-03 08:11:56.412: E/AndroidRuntime(5681): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
06-03 08:11:56.412: E/AndroidRuntime(5681): at dalvik.system.NativeStart.main(Native Method)
fragment_search_result_list.xml：
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context="com..SearchResultListActivity$PlaceholderFragment">
<ListView
android:id="@+id/listViewSearchResult"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
</ListView>
</LinearLayout>
activity_search_result_list.xml：
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
tools:context="com..SearchResultListActivity"
tools:ignore="MergeRootFrame"/>
答案 0 :(得分：2)
ListView属于Fragment Layout，当您在Activity onCreate调用的AsyncTask中初始化它时。
您可以在Fragment中初始化listview，也可以将片段布局设置为Activity。
我建议你在Fragment中初始化listview。要获取上下文，请使用getActivity()。
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_search_result_list, container, false);
list=(ListView)rootView.findViewById(R.id.listViewSearchResult);
new JSONParse(getActivity()).execute();
return rootView;
}
然后
Context mContext;
public JSONParse(Context context)
{
mContext= context;
}
然后
new SimpleAdapter(mContext...
执行阅读