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У меня есть одна проблема с изменением фрагментов, я использую spinner в панели действий, чтобы сделать это, а иногда и кнопку в alertdiaolog. И когда я нажимаю кнопку, у меня есть NullPointerException. Это мой код интерфейса обратного вызова:NullPointerException при изменении фрагмента и с использованием обратного вызова
public interface Callback {
public void load(String name);
}
И этот код моего первого фрагмента, я использую блесну в onCreateOptiontMenu:
private Callback callback;
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
Log.d("TAG", "onAttach");
try {
callback = (Callback) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString() + " must implement interface");
}
}
@Override
public void onDetach() {
super.onDetach();
callback = null;
}
public void onCreateOptionsMenu(Menu menu, MenuInflater inflate) {
menu.clear();
inflate.inflate(R.menu.kfu, menu);
spinner = (Spinner) menu.findItem(R.id.action_spinner).getActionView()
.findViewById(R.id.actionbar_spinner_change_map);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity()
.getBaseContext(),
android.R.layout.simple_spinner_dropdown_item, actions);
spinner.setAdapter(adapter);
spinner.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view,
int position, long id) {
Log.d("POSITION", "Position is = "+position);
switch (position) {
case 1:
if (parent.getItemAtPosition(position).equals("VKNews")) {
// Log.d("Tag", callback.toString()+" "+ (callback == null) + " " + parent.getItemAtPosition(position));
callback.load("VKNews"); //305 line
}
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
// TODO Auto-generated method stub
}
});
}
Во втором фрагменте я использую блесну, а иногда кнопку, чтобы изменить фрагмент:
private Callback callback;
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
Log.d("TAG", "onAttach");
try {
callback = (Callback) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString() + " must implement interface");
}
}
@Override
public void onDetach() {
super.onDetach();
callback = null;
}
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
...
if ((firstrun) || (account.access_token == null)) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Авторизация")
.setMessage(
"для просмотра новостей необходимо авторизоваться.")
.setCancelable(false)
.setPositiveButton("Авторизоваться",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int id) {
editor1.putInt("isVk", 1).commit();
editor1.apply();
startLoginActivity();
}
})
.setNegativeButton("Отмена",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,
int id) {
editor1.putInt("isVk", 0).commit();
editor1.apply();
Log.d("TAG", callback.toString());
callback.load("KFUNews");
Log.d("CHANGE", "change working");
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
// Save the state
getActivity()
.getSharedPreferences("PREFERENCE",
getActivity().MODE_PRIVATE).edit()
.putBoolean("firstrun", false).commit();
}
...
}
public void onCreateOptionsMenu(Menu menu, MenuInflater inflate) {
if (account.access_token != null || isChangedStat) {
inflate.inflate(R.menu.vk, menu);
spinner = (Spinner) menu.findItem(R.id.action_spinner1).getActionView()
.findViewById(R.id.actionbar_spinner_change_map);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity()
.getBaseContext(),
android.R.layout.simple_spinner_dropdown_item, actions);
spinner.setAdapter(adapter);
spinner.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view,
int position, long id) {
Log.d("POSITION", "" + parent.getItemAtPosition(position));
switch (position) {
case 1:
if (parent.getItemAtPosition(position).equals("KFUNews")) {
callback.load("KFUNews");
}
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
// TODO Auto-generated method stub
}
});
} else {
inflate.inflate(R.menu.vk1, menu);
spinner = (Spinner) menu.findItem(R.id.action_spinner1).getActionView()
.findViewById(R.id.actionbar_spinner_change_map);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity()
.getBaseContext(),
android.R.layout.simple_spinner_dropdown_item, actions);
spinner.setAdapter(adapter);
spinner.setOnItemSelectedListener(new OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view,
int position, long id) {
Log.d("POSITION", "" + parent.getItemAtPosition(position));
switch (position) {
case 1:
if (parent.getItemAtPosition(position).equals("KFUNews")) {
callback.load("KFUNews");
}
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
// TODO Auto-generated method stub
}
});
}
super.onCreateOptionsMenu(menu, inflate);
}
У меня есть nullpointer с первым фрагментом на 305 строке this callback.load ("VKNews");
Это мой журнал:
10-01 15:34:58.532: E/AndroidRuntime(2519): FATAL EXCEPTION: main
10-01 15:34:58.532: E/AndroidRuntime(2519): java.lang.NullPointerException
10-01 15:34:58.532: E/AndroidRuntime(2519): at ru.fosslabs.mobilestudent.fragment.KFUFragment$3.onItemSelected(KFUFragment.java:305)
10-01 15:34:58.532: E/AndroidRuntime(2519): at android.widget.AdapterView.fireOnSelected(AdapterView.java:892)
10-01 15:34:58.532: E/AndroidRuntime(2519): at android.widget.AdapterView.access$200(AdapterView.java:49)
10-01 15:34:58.532: E/AndroidRuntime(2519): at android.widget.AdapterView$SelectionNotifier.run(AdapterView.java:860)
10-01 15:34:58.532: E/AndroidRuntime(2519): at android.os.Handler.handleCallback(Handler.java:730)
10-01 15:34:58.532: E/AndroidRuntime(2519): at android.os.Handler.dispatchMessage(Handler.java:92)
10-01 15:34:58.532: E/AndroidRuntime(2519): at android.os.Looper.loop(Looper.java:137)
10-01 15:34:58.532: E/AndroidRuntime(2519): at android.app.ActivityThread.main(ActivityThread.java:5103)
10-01 15:34:58.532: E/AndroidRuntime(2519): at java.lang.reflect.Method.invokeNative(Native Method)
10-01 15:34:58.532: E/AndroidRuntime(2519): at java.lang.reflect.Method.invoke(Method.java:525)
10-01 15:34:58.532: E/AndroidRuntime(2519): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
10-01 15:34:58.532: E/AndroidRuntime(2519): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-01 15:34:58.532: E/AndroidRuntime(2519): at dalvik.system.NativeStart.main(Native Method)
мой Активность:
public class GeneralActivity extends Activity implements Callback {
...
@Override
public void load(String name) {
FragmentTransaction transaction = getFragmentManager()
.beginTransaction();
Log.d("TAG", "transaction = " + transaction + " "
+ (transaction == null));
if (name.equals("KFUNews")) {
transaction.replace(R.id.general_fragment, kfu);
transaction.commit();
invalidateOptionsMenu();
} else {
transaction.replace(R.id.general_fragment, vkfrag);
transaction.commit();
invalidateOptionsMenu();
}
}
}
Обновление: это не работает на Android 4.2.2 и 4.3, 4.4
осуществлять ли ваша деятельность интерфейс обратного вызова? –
да. public class GeneralActivity extends Activity реализует Callback { – metalink