我在这个论坛上尝试了不同的答案，这些答案与我的问题有关，但似乎没有一个适合我。
ArrayAdapter类
public class UserAdapter extends ArrayAdapter<User> {
public UserAdapter(Context context, ArrayList<User> users) {
super(context, 0, users);
}
private static class ViewHolder {
TextView water;
TextView amount;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
// Get the data item for this position
User user = getItem(position);
// Check if an existing view is being reused, otherwise inflate the view
ViewHolder viewHolder; // view lookup cache stored in tag
if (convertView == null) {
// If there's no view to re-use, inflate a brand new view for row
viewHolder = new ViewHolder();
LayoutInflater inflater = LayoutInflater.from(getContext());
convertView = inflater.inflate(R.layout.card, parent, false);
viewHolder.water = (TextView) convertView.findViewById(R.id.WaterConsumed);
viewHolder.amount = (TextView) convertView.findViewById(R.id.WaterAmount);
// Cache the viewHolder object inside the fresh view
convertView.setTag(viewHolder);
} else {
// View is being recycled, retrieve the viewHolder object from tag
viewHolder = (ViewHolder) convertView.getTag();
}
// Populate the data into the template view using the data object
viewHolder.water.setText(user.waterconsum);
viewHolder.amount.setText(user.amount);
// Return the completed view to render on screen
return convertView;
}
public class User implements Serializable{
String waterconsum;
String amount;
public User(String waterconsum, String amount) {
this.waterconsum = waterconsum;
this.amount = amount;
}
显示数据
的片段类之一public class WaterFragment extends Fragment {
ArrayList<User> arrayOfUsers = new ArrayList<User>();
UserAdapter adapter;
View view;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
setRetainInstance(true);
if (savedInstanceState != null) {
arrayOfUsers = (ArrayList<User>) savedInstanceState.getSerializable("List");
}
return view = inflater.inflate(R.layout.water, container, false);
}
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setRetainInstance(true);
Button button = (Button) view.findViewById(R.id.additem);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
showInputDialog();
}
});
adapter = new UserAdapter(getActivity(), arrayOfUsers);
ListView listView = (ListView) view.findViewById(R.id.listofitems);
if (listView.getAdapter() != null) {
listView.onRestoreInstanceState(savedInstanceState);
} else {
listView.setAdapter(adapter);
}
}
protected void showInputDialog() {
LayoutInflater layoutInflater = LayoutInflater.from(getActivity());
final View promptView = layoutInflater.inflate(R.layout.input_dialog, null);
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(getActivity());
alertDialogBuilder.setView(promptView);
final EditText editText = (EditText) promptView.findViewById(R.id.edittext);
alertDialogBuilder.setCancelable(false)
.setPositiveButton("Submit", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
String text = editText.getText().toString();
addItems(text);
}
})
.setNegativeButton("Cancel",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = alertDialogBuilder.create();
alert.show();
}
public void addItems(String text) {
arrayOfUsers.add(new User("Water Consumed Today", text));
}
@Override
public void onSaveInstanceState(Bundle state) {
state.putSerializable("List", arrayOfUsers);
super.onSaveInstanceState(state);
}
当我在不同的片段之间切换时，数组数据总是被重置。所以我不确定如何去解决这个问题，我已经尝试了各种解决方案，涉及保存片段状态和数组数据，但迄今为止似乎没有工作。
编辑:片段处理程序类
@Override
protected void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_calendar);
bottomBar = BottomBar.attach(this, savedInstanceState);
bottomBar.setItemsFromMenu(R.menu.three_buttons_menu, new OnMenuTabSelectedListener() {
@Override
public void onMenuItemSelected(@IdRes int menuItemId) {
if (menuItemId == R.id.Calendar) {
CalendarFragment f = new CalendarFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.frame, f).commit();
} else if (menuItemId == R.id.Water) {
WaterFragment wf = new WaterFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.frame,wf).commit();
} else if (menuItemId == R.id.Advice) {
AdviceFragment af = new AdviceFragment();
getSupportFragmentManager().beginTransaction().add(R.id.frame, af).commit();
} else if (menuItemId == R.id.Diary) {
AdviceFragment af = new AdviceFragment();
getSupportFragmentManager().beginTransaction().add(R.id.frame, af).commit();
} else if (menuItemId == R.id.Help) {
AdviceFragment af = new AdviceFragment();
getSupportFragmentManager().beginTransaction().add(R.id.frame, af).commit();
}
getFragmentManager().executePendingTransactions();
}
});
只在片段的onCreate中创建适配器一次。
并在onViewCreated中设置此适配器为listview。
private UserAdapter adapter;
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if(adapter==null)
adapter = new UserAdapter(getActivity(), arrayOfUsers);
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
ListView listView = (ListView) view.findViewById(R.id.listofitems);
listView.setAdapter(adapter);
}
并且每当数据发生变化时，在适配器中添加新项并调用notifyDataSetChanged。
UPDATE:从你的片段处理程序类，你正在创建新的实例，每次你是替换片段，如
CalendarFragment f = new CalendarFragment();
我建议你这样做……
private CalendarFragment calenderFragment;
private WaterFragment waterFragment;
private AdviceFragment adviceFragment;
@Override
protected void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_calendar);
calenderFragment = new CalendarFragment();
waterFragment = new WaterFragment();
adviceFragment = new AdviceFragment();
bottomBar = BottomBar.attach(this, savedInstanceState);
bottomBar.setItemsFromMenu(R.menu.three_buttons_menu, new OnMenuTabSelectedListener() {
@Override
public void onMenuItemSelected(@IdRes int menuItemId) {
if (menuItemId == R.id.Calendar) {
if(calenderFragment==null)
calenderFragment = new CalendarFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.frame, calenderFragment)
.commit();
} else if (menuItemId == R.id.Water) {
if(waterFragment==null)
waterFragment = new WaterFragment();
getSupportFragmentManager().beginTransaction().replace(R.id.frame, waterFragment)
.commit();
} else if (menuItemId == R.id.Advice) {
if(adviceFragment==null)
adviceFragment = new AdviceFragment();
getSupportFragmentManager().beginTransaction().add(R.id.frame, adviceFragment )
.commit();
} else if (menuItemId == R.id.Diary) {
if(adviceFragment==null)
adviceFragment = new AdviceFragment();
getSupportFragmentManager().beginTransaction().add(R.id.frame, adviceFragment )
.commit();
} else if (menuItemId == R.id.Help) {
if(adviceFragment==null)
adviceFragment = new AdviceFragment();
getSupportFragmentManager().beginTransaction().add(R.id.frame, adviceFragment )
.commit();
}
getFragmentManager().executePendingTransactions();
}
});