我正在尝试从mysql中检索数据并根据类别选项卡对其进行排序。当我打开尚未创建内容视图的活动时，我的应用程序崩溃。我可以知道这是什么问题吗？
03-10 04:12:49.043: E/AndroidRuntime(2251): FATAL EXCEPTION: main
03-10 04:12:49.043: E/AndroidRuntime(2251): java.lang.RuntimeException: Unable to start activity ComponentInfo{my.fyp.inticlassifieds/my.fyp.inticlassifieds.DisplayPostItem}: java.lang.IllegalStateException: Content view not yet created
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.app.ActivityThread.access$600(ActivityThread.java:141)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.os.Handler.dispatchMessage(Handler.java:99)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.os.Looper.loop(Looper.java:137)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.app.ActivityThread.main(ActivityThread.java:5103)
03-10 04:12:49.043: E/AndroidRuntime(2251): at java.lang.reflect.Method.invokeNative(Native Method)
03-10 04:12:49.043: E/AndroidRuntime(2251): at java.lang.reflect.Method.invoke(Method.java:525)
03-10 04:12:49.043: E/AndroidRuntime(2251): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
03-10 04:12:49.043: E/AndroidRuntime(2251): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
03-10 04:12:49.043: E/AndroidRuntime(2251): at dalvik.system.NativeStart.main(Native Method)
03-10 04:12:49.043: E/AndroidRuntime(2251): Caused by: java.lang.IllegalStateException: Content view not yet created
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.support.v4.app.ListFragment.ensureList(ListFragment.java:328)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.support.v4.app.ListFragment.getListView(ListFragment.java:222)
03-10 04:12:49.043: E/AndroidRuntime(2251): at my.fyp.inticlassifieds.BooksFragment.onCreateView(BooksFragment.java:87)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.support.v4.app.Fragment.performCreateView(Fragment.java:1500)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:927)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:570)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.app.Activity.performStart(Activity.java:5143)
03-10 04:12:49.043: E/AndroidRuntime(2251): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
03-10 04:12:49.043: E/AndroidRuntime(2251): ... 11 more
类别：
public class BooksFragment extends ListFragment {
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
JSONObject json;
ArrayList<Products> productsList = new ArrayList<Products>();
// url to get all products list
private static String url_all_products = "http://10.0.2.2:8000/project/display_items.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_PRODUCTS = "product";
private static final String TAG_PID = "pid";
private static final String TAG_NAME = "name";
private static final String TAG_BUDGET = "price";
private static final String TAG_DES = "description";
private static final String TAG_DATE_POSTED = "created_at";
private static final String TAG_CATEGORY = "category";
private static final String TAG_EMAIL = "email";
private static final String TAG_CONTACT = "contact";
// products JSONArray
JSONArray products = null;
ListView lv;
ListAdapter listadapter;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.list_fragment, container,
false);
productsList = new ArrayList<Products>();
lv = getListView();
// on seleting single product
// launching Edit Product Screen
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String pid = ((TextView) view.findViewById(R.id.pid)).getText()
.toString();
String name = ((TextView) view.findViewById(R.id.name))
.getText().toString();
String description = ((TextView) view.findViewById(R.id.des))
.getText().toString();
String price = ((TextView) view.findViewById(R.id.budget))
.getText().toString();
String date = ((TextView) view.findViewById(R.id.date_posted))
.getText().toString();
String category = ((TextView) view.findViewById(R.id.category))
.getText().toString();
String email = ((TextView) view
.findViewById(R.id.email_request)).getText().toString();
String contact = ((TextView) view
.findViewById(R.id.contact_request)).getText()
.toString();
// Starting new intent
Intent in = new Intent(getActivity(), DisplayItemInfo.class);
// sending information to next activity
in.putExtra(TAG_PID, pid);
in.putExtra(TAG_NAME, name);
in.putExtra(TAG_DES, description);
in.putExtra(TAG_BUDGET, price);
in.putExtra(TAG_DATE_POSTED, date);
in.putExtra(TAG_CATEGORY, category);
in.putExtra(TAG_EMAIL, email);
in.putExtra(TAG_CONTACT, contact);
startActivity(in);
}
});
new LoadAllProducts().execute();
return rootView;
}
class LoadAllProducts extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(getActivity());
pDialog.setMessage("Loading products. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All products from url
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
Intent intent = getIntent();
// getting attached intent data
String jsonS = intent.getStringExtra("JSon");
if (jsonS == null) {
// getting JSON string from URL
json = jParser.makeHttpRequest(url_all_products, "GET", params);
} else {
try {
JSONObject Jsonobj = new JSONObject(jsonS);
json = Jsonobj;
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
// Check your log cat for JSON reponse
Log.d("All Products: ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// products found
// Getting Array of Products
products = json.getJSONArray(TAG_PRODUCTS);
// looping through All Products
for (int i = 0; i < products.length(); i++) {
JSONObject c = products.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_PID);
String name = c.getString(TAG_NAME);
String budget = c.getString(TAG_BUDGET);
String description = c.getString(TAG_DES);
String category = c.getString(TAG_CATEGORY);
String contact = c.getString(TAG_CONTACT);
String email = c.getString(TAG_EMAIL);
String date = c.getString(TAG_DATE_POSTED);
if (category == "Books") {
// Create a new Product Obect, set its Values
Products mProduct = new Products();
mProduct.pid = id;
mProduct.name = name;
mProduct.price = budget;
mProduct.description = description;
mProduct.date = date;
mProduct.category = category;
mProduct.email = email;
mProduct.contact = contact;
// adding Product to ArrayList
productsList.add(mProduct);
}
}
} else {
// no products found
// Launch Add New product Activity
Intent i = new Intent(getActivity(), MainMenu.class);
// Closing all previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
private Intent getIntent() {
// TODO Auto-generated method stub
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all products
pDialog.dismiss();
if (productsList.size() > 0) {
/**
* Updating parsed JSON data into ListView
* */
CustomAdapter adapter = new CustomAdapter(getActivity(),
productsList);// ,
if (getListView() != null) {
// updating listview
setListAdapter(adapter);
} else {
Log.d("ListView-Reference", "ListView is null");
}
} else {
Log.d("Product List", "Products list is empty");
}
}
}
}
答案 0 :(得分：25)
onCreateView必须只返回代表片段的视图。 View上的其他操作应该在另一个回调onViewCreated：
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.list_fragment, container, false);
}
@Override
public void onViewCreated (View view, Bundle savedInstanceState) {
productsList = new ArrayList<Products>();
lv = getListView();
// on seleting single product
// launching Edit Product Screen
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String pid = ((TextView) view.findViewById(R.id.pid)).getText()
.toString();
String name = ((TextView) view.findViewById(R.id.name))
.getText().toString();
String description = ((TextView) view.findViewById(R.id.des))
.getText().toString();
String price = ((TextView) view.findViewById(R.id.budget))
.getText().toString();
String date = ((TextView) view.findViewById(R.id.date_posted))
.getText().toString();
String category = ((TextView) view.findViewById(R.id.category))
.getText().toString();
String email = ((TextView) view
.findViewById(R.id.email_request)).getText().toString();
String contact = ((TextView) view
.findViewById(R.id.contact_request)).getText()
.toString();
// Starting new intent
Intent in = new Intent(getActivity(), DisplayItemInfo.class);
// sending information to next activity
in.putExtra(TAG_PID, pid);
in.putExtra(TAG_NAME, name);
in.putExtra(TAG_DES, description);
in.putExtra(TAG_BUDGET, price);
in.putExtra(TAG_DATE_POSTED, date);
in.putExtra(TAG_CATEGORY, category);
in.putExtra(TAG_EMAIL, email);
in.putExtra(TAG_CONTACT, contact);
startActivity(in);
}
});
new LoadAllProducts().execute();
}
答案 1 :(得分：6)
您无法在getListView()中呼叫onCreateView()，因为ListView尚不存在。您需要将该代码放在onViewCreated()。
答案 2 :(得分：4)
您可以使用支票
来避免崩溃if(this.isAdded())
如果你在异常时调试那部分BooksFragment.getListView - 你会注意到它不存在。