意圖片段不工作

Question

我有困難發送意圖片段。我試圖將意圖從一個類發送到另一個類，然後爲片段發送setArgument。在片段中，我需要一個switch語句根據參數的值將數據設置到回收站視圖。

這是第一個活動（我只出在哪裏設置的意圖，在現實中有更多的孩子2位）：

expandableListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() { 
     @Override 
     public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) { 
      if (groupPosition == 0) { 
       if (childPosition == 0) { 
        Intent intent = new Intent(getApplicationContext(), WorkoutDaysActivity.class); 
        intent.putExtra("workout", "w29w1"); 
        startActivity(intent); 
       } 
       if (childPosition == 1) { 
        Intent intent = new Intent(getApplicationContext(), WorkoutDaysActivity.class); 
        intent.putExtra("workout", "w29w1"); 
        startActivity(intent); 
       } 

這裏是正在創建的片段，並在那裏我嘗試設置的參數：

public class WorkoutDaysActivity extends BaseActivity{ 

@Override 
protected void onCreate(@Nullable Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.workout_days); 
    mToolBar = activateToolbar(); 
    setUpNavigationDrawer(); 


    ViewPager vp = (ViewPager) findViewById(R.id.view_pager); 
    this.addPages(vp); 

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout); 
//  tabLayout.setTabGravity(TabLayout.GRAVITY_FILL); 
    tabLayout.setupWithViewPager(vp); 
    tabLayout.setOnTabSelectedListener(listener(vp)); 

} 
private void addPages(ViewPager pager) { 
    MyFragPagerAdapter adapter = new MyFragPagerAdapter(getSupportFragmentManager()); 
    Intent intent = getIntent(); 
    String workout = intent.getStringExtra("workout"); 
    Bundle args = new Bundle(); 
    args.putString("workout", workout); 

    MondayFragment mondayFragment = new MondayFragment(); 
    mondayFragment.setArguments(args); 
    adapter.addPage(mondayFragment); 
    WedFragment wedFragment = new WedFragment(); 
    wedFragment.setArguments(args); 
    adapter.addPage(wedFragment); 
    FridayFragment fridayFragment = new FridayFragment(); 
    fridayFragment.setArguments(args); 
    adapter.addPage(fridayFragment); 

最後這裏是三個片段類，我嘗試使用switch語句設定值中的一個：

public class WedFragment extends Fragment { 

Bundle args = getArguments(); 
String workout3 = args.getString("workout"); 

@Nullable 
@Override 
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { 
    View view = inflater.inflate(R.layout.wed_fragment, null); 

//  //RECYCLERVIEW 
    RecyclerView rv = (RecyclerView) view.findViewById(R.id.mRecyclerWed); 
    rv.setLayoutManager(new LinearLayoutManager(this.getActivity())); 
    rv.setAdapter(new MyRecyclerAdapter(this.getActivity(), getWedWorkout())); 

    return view; 


} 

private ArrayList<Workout> getWedWorkout() { 
    //COLLECTION OF MONDAY WORKOUT 

    ArrayList<Workout> workout = new ArrayList<>(); 
    switch(workout3) { 
     case "w29w1" : { 
      Workout workouts = new Workout("Bench", "60", "6", "155", false); 

      //ADD TO COLLECTION 
      workout.add(workouts); 

      workouts = new Workout("Bench", "70", "5", "175", false); 
      workout.add(workouts); 

      break;} 
     case "w29w2" :{ 
      Workout workouts = new Workout("Squat", "60", "6", "155", false); 

      //ADD TO COLLECTION 
      workout.add(workouts); 

      workouts = new Workout("Squat", "70", "5", "175", false); 
      workout.add(workouts); 

     break;} 
    } return workout; 

這裏是崩潰的應用程序錯誤：

08-03 13:53:11.917 32143-32143/com.bestworkouts.sheikoworkout E/AndroidRuntime: FATAL EXCEPTION: main 
                      Process: com.bestworkouts.sheikoworkout, PID: 32143 
                      java.lang.RuntimeException: Unable to start activity ComponentInfo{com.bestworkouts.sheikoworkout/com.bestworkouts.sheikoworkout.WorkoutDaysActivity}: 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:3254) 
                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3350) 
                       at android.app.ActivityThread.access$1100(ActivityThread.java:222) 
                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795) 
                       at android.os.Handler.dispatchMessage(Handler.java:102) 
                       at android.os.Looper.loop(Looper.java:158) 
                       at android.app.ActivityThread.main(ActivityThread.java:7229) 
                       at java.lang.reflect.Method.invoke(Native Method) 
                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) 
                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) 
                      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 com.bestworkouts.sheikoworkout.Fragments.WedFragment.<init>(WedFragment.java:24) 
                       at com.bestworkouts.sheikoworkout.WorkoutDaysActivity.addPages(WorkoutDaysActivity.java:47) 
                       at com.bestworkouts.sheikoworkout.WorkoutDaysActivity.onCreate(WorkoutDaysActivity.java:27) 
                       at android.app.Activity.performCreate(Activity.java:6876) 
                       at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1135) 
                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3207) 
                       at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3350)  
                       at android.app.ActivityThread.access$1100(ActivityThread.java:222)  
                       at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)  
                       at android.os.Handler.dispatchMessage(Handler.java:102)  
                       at android.os.Looper.loop(Looper.java:158)  
                       at android.app.ActivityThread.main(ActivityThread.java:7229)  
                       at java.lang.reflect.Method.invoke(Native Method)  
                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)  
                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)  

哪裏WedFragment.java:24是這一行：

String workout3 = args.getString("workout"); 

WorkoutDaysActivity.java:47是這一行：

WedFragment wedFragment = new WedFragment(); 

and WorkoutDaysActivity.java:27 is this line：

tabLayout.setupWithViewPager(vp); 

Answer 1

把這兩行您的onCreate函數中：

public class WedFragment extends Fragment { 

Bundle args; 
String workout3=""; 

@Nullable 
@Override 
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { 
    args = getArguments(); 
    workout3 = args.getString("workout"); 
    View view = inflater.inflate(R.layout.wed_fragment, null); 

    //RECYCLERVIEW 
    RecyclerView rv = (RecyclerView) view.findViewById(R.id.mRecyclerWed); 
    rv.setLayoutManager(new LinearLayoutManager(this.getActivity())); 
    rv.setAdapter(new MyRecyclerAdapter(this.getActivity(), getWedWorkout())); 

    return view; 
}