[英]Fragment's onCreateView called before activity's onCreate
我有我的VehicleListActivity ，它将Bundle传递给我的片段。 这是活动的onCreate方法：
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_vehicle_list);
vehicles = new ArrayList<>();
Intent intent = getIntent();
String userID = intent.getStringExtra("userID");
LoadingVehicleListFragment f = new LoadingVehicleListFragment();
Bundle fArguments = new Bundle();
fArguments.putString("userID", userID);
f.setArguments(fArguments);
getSupportFragmentManager().beginTransaction().add(R.id.loadingVehicleFragment, f).commit();
}
这是片段的onCreateView ：
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
activity = (VehicleListActivity)getActivity();
context = activity;
listener = activity;
String userID = getArguments().getString("userID");
getUserInformation(userID);
return inflater.inflate(com.devspark.progressfragment.R.layout.fragment_progress, container, false);
}
我注意到片段的onCreateView在活动的onCreate之前被调用，因此片段中的getArguments()返回null，这将导致null指针异常。 我应该在片段中的哪里放置getArguments()以避免发生此异常？
编辑：根据要求，这是整个片段的来源：
public class LoadingVehicleListFragment extends ProgressFragment
{
private VehicleListListener listener;
private VehicleListActivity activity;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
return inflater.inflate(com.devspark.progressfragment.R.layout.fragment_progress, container, false);
}
/*@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState)
{
super.onActivityCreated(savedInstanceState);
int c = 0;
listener = (VehicleListActivity)getActivity();
getUserInformation(getArguments().getString("userID"));
}*/
private void getUserVehicles(String userID)
{
Response.Listener<String> responseListener = new Response.Listener<String>()
{
@Override
public void onResponse(String response)
{
try
{
HashMap resultMap = new ObjectMapper().readValue(response, HashMap.class);
VehicleListRequest.ErrorCode errorCode = VehicleListRequest.ErrorCode.fromInt(Integer.parseInt(resultMap.get("error_code").toString()));
switch (errorCode)
{
case NONE:
parseVehicleFromMap(resultMap);
break;
case EXCEPTION_CAUGHT:
AlertDialog.Builder builder2 = new AlertDialog.Builder(getActivity());
builder2.setMessage("Eccezione catturata. \n Messaggio: " + resultMap.get("error_message"));
builder2.create().show();
break;
}
}
catch (IOException e)
{
// TODO gestire
e.printStackTrace();
}
}
};
VehicleListRequest request = new VehicleListRequest(userID, responseListener, null);
RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
requestQueue.add(request);
}
public void getUserInformation(final String userID)
{
Response.Listener<String> responseListener = new Response.Listener<String>()
{
@Override
public void onResponse(String response)
{
try
{
HashMap resultMap = new ObjectMapper().readValue(response, HashMap.class);
GetUserRequest.ErrorCode errorCode = GetUserRequest.ErrorCode.fromInt(Integer.parseInt(resultMap.get("error_code").toString()));
switch (errorCode)
{
case NONE:
listener.setLoggedUser(User.fromMap(resultMap));
getUserVehicles(userID);
break;
case EXCEPTION_CAUGHT:
AlertDialog.Builder builder2 = new AlertDialog.Builder(getActivity());
builder2.setMessage("Eccezione catturata. \n Messaggio: " + resultMap.get("error_message"));
builder2.create().show();
break;
}
}
catch (IOException e)
{
// TODO gestire
e.printStackTrace();
}
}
};
GetUserRequest request = new GetUserRequest(userID, responseListener, null);
RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
requestQueue.add(request);
}
private void parseVehicleFromMap(HashMap map)
{
int i = 0;
while (map.containsKey(String.valueOf(i)))
{
final Vehicle v = new Vehicle();
HashMap vehicleMap = (HashMap) map.get(String.valueOf(i));
v.setPlate(vehicleMap.get("plate").toString());
v.setKm(vehicleMap.get("km") == null ? null : Integer.parseInt(vehicleMap.get("km").toString()));
v.setInUse(Integer.parseInt(vehicleMap.get("in_use").toString()) == 1);
v.setFuelQuantity(Double.parseDouble(vehicleMap.get("actual_fuel_quantity").toString()));
v.setEffectiveFuelEconomy(Double.parseDouble(vehicleMap.get("effective_fuel_economy").toString()));
v.setInsuranceDate(vehicleMap.get("insurance_date") == null ? null : new LocalDate(vehicleMap.get("insurance_date").toString()));
v.setMatriculationDate(new LocalDate(vehicleMap.get("matriculation_date").toString()));
v.setLatitude(vehicleMap.get("latitude") == null ? null : Double.parseDouble(vehicleMap.get("latitude").toString()));
v.setLongitude(vehicleMap.get("longitude") == null ? null : Double.parseDouble(vehicleMap.get("longitude").toString()));
v.setUser(activity.getLogged());
listener.addVehicle(v);
i++;
}
}
} // end class
这是错误日志：
03-27 18:30:47.274 4966-4966/clyky.cartracker E/AndroidRuntime: FATAL EXCEPTION: main
Process: clyky.cartracker, PID: 4966
java.lang.RuntimeException: Unable to start activity ComponentInfo{clyky.cartracker/clyky.cartracker.activities.VehicleListActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2434)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2504)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1347)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5458)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
at clyky.cartracker.activities.fragments.LoadingVehicleListFragment.onActivityCreated(LoadingVehicleListFragment.java:51)
at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:2193)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1323)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1523)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1585)
at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:2832)
at android.support.v4.app.FragmentController.dispatchActivityCreated(FragmentController.java:201)
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:603)
at android.support.v7.app.AppCompatActivity.onStart(AppCompatActivity.java:181)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1237)
at android.app.Activity.performStart(Activity.java:6268)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2397)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2504)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1347)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5458)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
在这些例外之前，我还遇到了一些“联名交易失败”，例如：
03-27 18:30:41.955 1452-1452/com.google.android.inputmethod.latin E/JavaBinder: !!! FAILED BINDER TRANSACTION !!! (parcel size = 100)
03-27 18：30：41.956 1452-1452 / com.google.android.inputmethod.latin E / AndroidIME：aqx：java.lang.RuntimeException：android.os.DeadObjectException：小宗包裹交易失败； 远程进程可能死了03-27 18：30：41.999 1452-1452 / com.google.android.inputmethod.latin E / JavaBinder：!!! 绑定交易失败！！！ （包裹大小= 100）03-27 18：30：42.000 1452-1452 / com.google.android.inputmethod.latin E / AndroidIME：aqx：java.lang.RuntimeException：android.os.DeadObjectException：小包裹交易失败; 远程进程可能死了03-27 18：30：42.001 1452-1452 / com.google.android.inputmethod.latin E / JavaBinder：!!! 绑定交易失败！！！ （包裹大小= 100）03-27 18：30：42.002 1452-1452 / com.google.android.inputmethod.latin E / AndroidIME：aqx：java.lang.RuntimeException：android.os.DeadObjectException：小包裹交易失败; 远程进程可能死了03-27 18：30：42.005 1452-1452 / com.google.android.inputmethod.latin E / JavaBinder：!!! 绑定交易失败！！！ （包裹大小= 100）03-27 18：30：42.007 1452-1452 / com.google.android.inputmethod.latin E / AndroidIME：aqx：java.lang.RuntimeException：android.os.DeadObjectException：小包裹交易失败; 远程进程可能死了03-27 18：30：42.008 1452-1452 / com.google.android.inputmethod.latin E / JavaBinder：!!! 绑定交易失败！！！ （包裹大小= 100）03-27 18：30：42.010 1452-1452 / com.google.android.inputmethod.latin E / AndroidIME：aqx：java.lang.RuntimeException：android.os.DeadObjectException：小包裹上的交易失败; 远程进程可能死了03-27 18：30：42.026 1452-5094 / com.google.android.inputmethod.latin E / JavaBinder：!!! 绑定交易失败！！！ （包裹大小= 168）03-27 18：30：42.031 1452-5095 / com.google.android.inputmethod.latin E / JavaBinder：!!! 绑定交易失败！！！ （包裹大小= 168）03-27 18：30：43.509 1452-1452 / com.google.android.inputmethod.latin E / JavaBinder：!!! 绑定交易失败！！！ （包裹大小= 100）03-27 18：30：43.510 1452-1452 / com.google.android.inputmethod.latin E / AndroidIME：aqx：java.lang.RuntimeException：android.os.DeadObjectException：小包裹交易失败; 远程进程可能死了03-27 18：30：43.510 1452-1452 / com.google.android.inputmethod.latin E / JavaBinder：!!! 绑定交易失败！！！ （包裹大小= 100）03-27 18：30：43.512 1452-1452 / com.google.android.inputmethod.latin E / AndroidIME：aqx：java.lang.RuntimeException：android.os.DeadObjectException：小包裹交易失败; 远程进程可能死了03-27 18：30：43.542 1452-5121 / com.google.android.inputmethod.latin E / JavaBinder：!!! 绑定交易失败！！！ （包裹大小= 168）03-27 18：30：43.547 1452-5120 / com.google.android.inputmethod.latin E / JavaBinder：!!! 绑定交易失败！！！ （包裹大小= 168）
但是，它们开始出现在引发异常的操作之前，因此我认为这些错误没有影响。
创建主机活动时，将在onCreateView()方法之后调用onActivityCreated() 。 活动和片段实例以及活动的视图层次结构已创建。 此时，可以使用findViewById()方法访问视图。 例。 在这种方法中，您可以实例化需要Context对象的对象。
尝试在那里访问它，也不getActivity()上下文存储在片段中，请始终调用getActivity()
空指针是由android框架onCreateView()的执行流引起的。当该片段第一次绘制其用户界面时，系统将调用此回调。 要为片段绘制UI，必须从此方法返回一个View组件，该组件是片段布局的根。 如果片段不提供UI，则可以返回null。 因此，它首先被调用，因此给出了空指针异常。
你可以试试这个吗？
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_vehicle_list);
vehicles = new ArrayList<>();
String userID;
Bunlde bundle = getIntent().getExtras();
if(bundle != null){
userID = bundle.getString("userID");
}
if(savedInstanceState == null){
LoadingVehicleListFragment f = new LoadingVehicleListFragment();
Bundle fArguments = new Bundle();
fArguments.putString("userID", userID);
f.setArguments(fArguments);
getSupportFragmentManager().beginTransaction().replace(R.id.loadingVehicleFragment, f).commit();
}
}
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