方向更改后片段为空

Question

我的Fragments 有问题。我有四个处于 portrait 模式的片段。

设置片段

public void setCorrectNavigationItem(int id) {
    if (id == R.id.nav_auftragsbilder) {
        fragment = new AuftragsbilderFragment();
        id = R.id.nav_auftragsbilder;
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    } else if (id == R.id.nav_auftragskorrektur) {
        fragment = new AuftragskorrekturFragment();
        id = R.id.nav_auftragskorrektur;
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    } else if (id == R.id.nav_lagerplatz) {
        fragment = new LagerplatzFragment();
        id = R.id.nav_lagerplatz;
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
    } else if (id == R.id.nav_biegenstatus) {
        fragment = new BiegestatusFragment();
        id = R.id.nav_biegenstatus;
        setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
    }
    _navigationView.setCheckedItem(id);
    _selectedMenuItem = id;

    SharedPreferences.Editor editor = menuCheck.edit();
    editor.putInt("id", id);
    editor.commit();

    //Fragment öffnen
    if (fragment != null) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction ft = fragmentManager.beginTransaction();
        ft.replace(R.id.fragment_container, fragment);
        ft.commit();
    }
}

所以在我的片段设置方法中，我现在必须为每个不同的片段设置方向。我不得不将我的 'BiegestatusFragment' 更改为 landscape，在那里我调用了一个扫描条形码的方法，intent result 我在我的 Fragment 中设置了参数。

这是我的条形码扫描Activity

//Biegestatus Begleitschein-Barcodes
public void makeBiegestatusBegleitscheinBarcode() {
    _lastAction = ACTION_BIEGESTATUS_BEGLEITSCHEIN_BARCODE;
    if (!checkCameraPermission(this, PERMISSIONS)) {
        ActivityCompat.requestPermissions(this, PERMISSIONS, PERMISSION_ALL);
    } else {
        Intent intent = new Intent(this, ContinuousCaptureActivity.class);
        startActivityForResult(intent, 1);
    }
}

意图结果

protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (data != null) {
        ArrayList<String> begleitscheine = data.getStringArrayListExtra("begleitscheine");
        if (resultCode == 1 && begleitscheine != null) {
            //HERE IT IS NULL
            ((BiegestatusFragment) fragment).setBegleitscheine(begleitscheine);
        } else {
            Toast.makeText(this, "Scannen abgebrochen", Toast.LENGTH_LONG).show();
        }
    } else {
        Toast.makeText(this, "Unbekannter Fehler aufgetreten, Entwickler kontaktieren.", Toast.LENGTH_LONG).show();
    }
}

CreateView 上的片段

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment_biegestatus, container, false);

    _cardEdit = (EditText) v.findViewById(R.id.workerEdit);
    _scrollViewArticles = (ScrollView) v.findViewById(R.id.scrollViewArticles);
    _searchImageLayout = (LinearLayout) v.findViewById(R.id.searchImageLayout);
    _personalNummer = (EditText) v.findViewById(R.id.workerEdit);
    _progressBar = (LinearLayout) v.findViewById(R.id.progressBar);
    _maschinenPicker = (NumberPicker) v.findViewById(R.id.maschinenPicker);
    _pickerHolder = (LinearLayout) v.findViewById(R.id.pickerHolder);
    _scanBegleitscheinBtn = (Button) v.findViewById(R.id.scanBegleitscheinBtn);

    return v;
}

方法应该被调用

public void setBegleitscheine(ArrayList<String> begleitscheine) {
    _begleitscheine = begleitscheine;
}

现在我的 Fragment 为空，因为 orientation 发生了变化。 删除方向设置方法解决了我的问题。但我需要把这个片段放在风景中。

错误

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: at.co.era.bilder.erabilderapp, PID: 21835
                  java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=1, data=Intent {  launchParam=MultiScreenLaunchParams { mDisplayId=0 mBaseDisplayId=0 mFlags=0 }(has extras) }} to activity {at.co.era.bilder.erabilderapp/at.co.era.bilder.erabilderapp.HomeActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void at.co.era.bilder.erabilderapp.BiegestatusFragment.setBegleitscheine(java.util.ArrayList)' on a null object reference
                      at android.app.ActivityThread.deliverResults(ActivityThread.java:4520)
                      at android.app.ActivityThread.handleSendResult(ActivityThread.java:4563)
                      at android.app.ActivityThread.-wrap22(ActivityThread.java)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1698)
                      at android.os.Handler.dispatchMessage(Handler.java:102)
                      at android.os.Looper.loop(Looper.java:154)
                      at android.app.ActivityThread.main(ActivityThread.java:6776)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1496)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1386)
                   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void at.co.era.bilder.erabilderapp.BiegestatusFragment.setBegleitscheine(java.util.ArrayList)' on a null object reference
                      at at.co.era.bilder.erabilderapp.HomeActivity.onActivityResult(HomeActivity.java:1130)
                      at android.app.Activity.dispatchActivityResult(Activity.java:7280)
                      at android.app.ActivityThread.deliverResults(ActivityThread.java:4516)
                      at android.app.ActivityThread.handleSendResult(ActivityThread.java:4563) 
                      at android.app.ActivityThread.-wrap22(ActivityThread.java) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1698) 
                      at android.os.Handler.dispatchMessage(Handler.java:102) 
                      at android.os.Looper.loop(Looper.java:154) 
                      at android.app.ActivityThread.main(ActivityThread.java:6776) 
                      at java.lang.reflect.Method.invoke(Native Method) 
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1496) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1386) 

Answer 1

 //Fragment öffnen
    if (fragment != null) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction ft = fragmentManager.beginTransaction();
        ft.replace(R.id.fragment_container, fragment);
        ft.addToBackStack(null); // or you can give it any name instead of null to get the frament when poping the fragment from backstack
        ft.commit();
    }

Answer 2

您可以通过将清单中的以下行添加到您的活动标签来强制您的活动在方向更改后不重新加载

android:configChanges="orientation" 

Answer 3

在片段内部，在 onCreateView() 中尝试使用：

setRetainInstance(true);

在此处查看文档： https://developer.android.com/reference/android/app/Fragment#setRetainInstance(boolean)