我很难解决这个问题。我正在尝试将三个不同的自定义对象的arraylists发送到可扩展列表视图单击的片段。这里是可扩展的列表视图代码（我只包括第一组的位置和子项，但实际上还有更多）：
*/
public class MyWorkout extends BaseActivity{
ExpandableListView expandableListView;
HashMap<String, List<String>> Workouts_details;
List<String> Workout_list;
WorkoutsAdapter mAdapter;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.my_workout);
mToolBar = activateToolbar();
setUpNavigationDrawer();
expandableListView = (ExpandableListView) findViewById(R.id.listViewWorkouts);
Workouts_details = DataProvider.getInfo();
Workout_list = new ArrayList<>(Workouts_details.keySet());
mAdapter = new WorkoutsAdapter(this, Workouts_details, Workout_list);
expandableListView.setAdapter(mAdapter);
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);
}
从那里，每个childClick将应用程序发送到WorkoutDaysActivity，其中3个选项卡设置了片段。这是这个类的代码：
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));
}
//ADD ALL PAGES
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);
pager.setAdapter(adapter);
}
private TabLayout.OnTabSelectedListener listener(final ViewPager pager) {
return new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
pager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
}
};
}
}
然后从那里，我有3个选项卡片段类。每个班级都是这样的：
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;
//SINGLE EXERCISE
}
@Override
public String toString() {
return "Wednesday";
}
}
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)
答案 0 :(得分：1)
我们在您的代码中尝试将ArrayList对象发送到Fragment的位置尚不清楚 - 但我建议您将您的课程（Workout）设为延长Parcelable ，然后发送ArrayList<Workout> - 您可以使用putParcelableArrayList(String key, ArrayList<? extends Parcelable> value)类的Bundle方法签名，然后设置Bundle作为fragment.setArguments(Bundle)方法的参数。基本上，你将拥有这样的代码：
ArrayList<Workout> workoutList = new ArrayList<Workout>();
workoutList.add(<some-workout-object>)
Bundle bundle = new Bundle();
bundle.putParcelableArrayList("mondayWorkoutList", workoutList);
Fragment fragment = new MondayFragment();
fragment.setArguments(bundle);
查看Fragment tutorial有关如何使用Bundle将参数发送到Fragment的示例。您可能还想查看API documentation for Bundle class
我希望这会有所启发。
答案 1 :(得分：0)
作为一种解决方法，有时很容易将数组列表转换为字符串（或JSON字符串）并通过
发送bundle.putString()
然后在片段中将字符串解析回数组列表。