问题
I have asynctask that gathers usernames, comments, and numbers. It places them into strings and is then suppose to call a BaseAdapter class, create an adapter, and set the adapter to the class. But my code doesn't work, it crashes the app, here is my code
public class DashboardActivity extends ListActivity {
String comments[];
String usernames[];
String numbers[];
ListView lstComments;
class CreateCommentLists extends BaseAdapter{
Context ctx_invitation;
String[] listComments;
String[] listNumbers;
String[] listUsernames;
public CreateCommentLists(String[] comments, String[] usernames, String[] numbers)
{
super();
listComments = comments;
listNumbers = usernames;
listUsernames = numbers;
}
@Override
public int getCount() {
if(null == listComments)
{
return 0;
}
// TODO Auto-generated method stub
return listComments.length;
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return listComments[position];
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
View v = null;
try
{
String inflater = Context.LAYOUT_INFLATER_SERVICE;
LayoutInflater li = (LayoutInflater)ctx_invitation.getSystemService(inflater);
v = li.inflate(R.layout.list_item, null);
TextView commentView = (TextView)v.findViewById(R.id.listComment);
TextView NumbersView = (TextView)v.findViewById(R.id.listNumber);
TextView usernamesView = (TextView)v.findViewById(R.id.listPostedBy);
commentView.setText(listComments[position]);
NumbersView.setText(listNumbers[position]);
usernamesView.setText(listUsernames[position]);
}
catch(Exception e)
{
e.printStackTrace();
}
return v;
}
}
class loadComments extends AsyncTask<JSONObject, String, JSONObject> {
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
}
protected JSONObject doInBackground(JSONObject... params) {
JSONObject json2 = CollectComments.collectComments(usernameforcomments, offsetNumber);
return json2;
}
@Override
protected void onPostExecute(JSONObject json2) {
try {
if (json2.getString(KEY_SUCCESS) != null) {
registerErrorMsg.setText("");
String res2 = json2.getString(KEY_SUCCESS);
if(Integer.parseInt(res2) == 1){
JSONArray commentArray = json2.getJSONArray(KEY_COMMENT);
String comments[] = new String[commentArray.length()];
for ( int i=0; i<commentArray.length(); i++ ) {
comments[i] = commentArray.getString(i);
}
JSONArray numbersArray = json2.getJSONArray(KEY_NUMBER);
String numbers[] = new String[numbersArray.length()];
for ( int i=0; i<numbersArray.length(); i++ ) {
numbers[i] = numbersArray.getString(i);
}
JSONArray usernameArray = json2.getJSONArray(KEY_USERNAME);
String usernames[] = new String[usernameArray.length()];
for ( int i=0; i<usernameArray.length(); i++ ) {
usernames[i] = usernameArray.getString(i);
}
CreateCommentLists mycmlist = new CreateCommentLists(comments, usernames, numbers);
lstComments = (ListView)findViewById(android.R.id.list);
lstComments.setAdapter(mycmlist);
}//end if key is == 1
else{
// Error in registration
registerErrorMsg.setText(json2.getString(KEY_ERROR_MSG));
}//end else
}//end if
} //end try
catch (JSONException e) {
e.printStackTrace();
}//end catch
}
}
new loadComments().execute();
}
Here is my logCat
07-17 17:07:13.436: E/AndroidRuntime(23880): FATAL EXCEPTION: main
07-17 17:07:13.436: E/AndroidRuntime(23880): java.lang.NullPointerException
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.ListView.measureScrapChild(ListView.java:1163)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.ListView.measureHeightOfChildren(ListView.java:1294)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.ListView.onMeasure(ListView.java:1155)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1369)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.measureVertical(LinearLayout.java:660)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.RelativeLayout.measureChild(RelativeLayout.java:579)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:392)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1369)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1017)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.onMeasure(LinearLayout.java:555)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.measureVertical(LinearLayout.java:812)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-17 17:07:13.436: E/AndroidRuntime(23880): at com.navdrawer.SimpleSideDrawer.onMeasure(SimpleSideDrawer.java:443)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4706)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
07-17 17:07:13.436: E/AndroidRuntime(23880): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2162)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.View.measure(View.java:13011)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1091)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2505)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.os.Handler.dispatchMessage(Handler.java:99)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.os.Looper.loop(Looper.java:154)
07-17 17:07:13.436: E/AndroidRuntime(23880): at android.app.ActivityThread.main(ActivityThread.java:4945)
07-17 17:07:13.436: E/AndroidRuntime(23880): at java.lang.reflect.Method.invokeNative(Native Method)
07-17 17:07:13.436: E/AndroidRuntime(23880): at java.lang.reflect.Method.invoke(Method.java:511)
07-17 17:07:13.436: E/AndroidRuntime(23880): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
07-17 17:07:13.436: E/AndroidRuntime(23880): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
07-17 17:07:13.436: E/AndroidRuntime(23880): at dalvik.system.NativeStart.main(Native Method)
回答1:
Have you checked if the View v that you return from your getView() method is null? Catching Exception catches all exceptions. Not really helpful in my opinion. What's happening here is that you have not initiated Context ctx_invitation. You should do this in the constructor. Now, since ctx_invitation is null, it causes a NullPointerException which is caught by the catch block. and View v remains null.
Change the constructor for CreateCommentLists:
public CreateCommentLists(String[] comments, String[] usernames, String[] numbers, DashboardActivity context)
{
super();
listComments = comments;
listNumbers = usernames;
listUsernames = numbers;
ctx_invitation = context;
}
Change the following as well:
CreateCommentLists mycmlist = new CreateCommentLists(comments, usernames, numbers, DashboardActivity.this);
回答2:
I hope this might be help,
onPostExecute include (Inside AsyncTask)
ExampleAdapter sectionedAdapter = new EfficientAdapter(ClassInfoThread.this,getBaseContext()); listView.setAdapter(sectionedAdapter);
and in your adapter class add this constructor
public ExampleAdapter(ExampleThread exampleThread,Context context) { mInflater = LayoutInflater.from(context); }
good luck.
Nandakishore P
回答3:
Now ctx_invitation is never assigned a value. You probably need a constructor to assign value to ctx_invitation.
回答4:
Googling around, looking at this question looks like you might be returning a null view from your adapter's getView method. Try tossing some breakpoints into the getView method and figure out where you are returning a null view.
Also, where are you storing the reference to the ctx_invitation in your BaseAdapter.
In the constructor you might want to pass that in
来源：https://stackoverflow.com/questions/17710252/baseadapter-class-wont-setadapter-inside-asynctask-android