我使用片段在recyclerview中的sqlite数据库中显示数据。我设置了一个textView，如果在arraylist.size（）== 0，它将显示一条消息，如果不是，它将不显示。问题是即使数据库中有数据，arraylist.size（）也总是返回零。
在向数据库添加数据时，我使用此
add.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
TextView errorWeight = (TextView)weight.getSelectedView();
TextView errorPer = (TextView)per.getSelectedView();
TextView errorRepeat = (TextView)repeat.getSelectedView();
if (name_food.getText().toString().trim().equalsIgnoreCase("")) {
name_food.setError("Please add a title to the task");
}
else if (date.getText().toString().trim().equalsIgnoreCase("")) {
date.setError("Set date to start");
}
else if (time.getText().toString().trim().equalsIgnoreCase("")) {
time.setError("Set time to start");
}
else if (quantity.getText().toString().trim().equalsIgnoreCase("")) {
quantity.setError("Set amount of food");
}
else if (weight.getSelectedItem().toString().trim().equalsIgnoreCase("Weight")) {
errorWeight.setError("Set weight of food");
}
else if (per.getSelectedItem().toString().trim().equalsIgnoreCase("Per")) {
errorPer.setError("Set Per meal or per day");
}
else if (repeat.getSelectedItem().toString().trim().equalsIgnoreCase("Repeat Task after")) {
errorRepeat.setError("Set task repetition");
}
else
{
name_food.setError(null);
date.setError(null);
time.setError(null);
quantity.setError(null);
errorWeight.setError(null);
errorPer.setError(null);
errorRepeat.setError(null);
arrayLists=new ArrayList<>();
food_model item=new food_model();
db=new food_database(add_food.this);
adapter=new foodRecyclerAdapter(add_food.this,arrayLists);
item.setPet_id(Integer.valueOf(petid.getText().toString()));
item.setPet_name(name_pet.getText().toString());
item.setType_food(name_food.getText().toString());
item.setDate(date.getText().toString());
item.setTime(time.getText().toString());
item.setQuantity(quantity.getText().toString());
item.setFood_weight(weight.getSelectedItem().toString());
item.setMeal(per.getSelectedItem().toString());
item.setNote(note.getText().toString());
item.setSched(repeat.getSelectedItem().toString());
boolean addfood=db.insertDataTofood(item);
if(addfood)
{
adapter.addItem(item);
Toast.makeText(add_food.this,"Task has been added",Toast.LENGTH_SHORT).show();
Toast.makeText(add_food.this,"Item added"+arrayLists.size(),Toast.LENGTH_SHORT).show();
Intent intent=new Intent(add_food.this,foodActivity.class);
intent.putExtra("name",name);
intent.putExtra("id",id);
intent.putExtra("breed",breed);
intent.putExtra("type",type);
startActivity(intent);
finish();
}
else
{
Toast.makeText(add_food.this,"Task not added",Toast.LENGTH_SHORT).show();
}
}
}
});
然后在Recyclerview适配器中，我使用此方法将数据添加到arraylist
public void addItem(food_model item) {
foodarraylist.add(0, item);
notifyItemInserted(0);
}
然后是片段
public class food_sched extends Fragment {
FloatingActionButton floatingActionButton;
RecyclerView recyclerView;
TextView reminder,subreminder;
Context context;
ArrayList<food_model> model;
Cursor c;
foodRecyclerAdapter adapter;
LinearLayoutManager linearLayoutManager;
String name,id,type,breed;
public food_sched() {
// Required empty public constructor
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
model=new ArrayList<>();
Intent taker=getActivity().getIntent();
name=taker.getStringExtra("name");
id=taker.getStringExtra("id");
type=taker.getStringExtra("type");
breed=taker.getStringExtra("breed");
context=getActivity();
if(model.size()==0)
{
Toast.makeText(context,"size is "+model.size(),Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(context,"size is "+model.size(),Toast.LENGTH_SHORT).show();
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view= inflater.inflate(R.layout.frag_food_sched, container, false);
recyclerView=(RecyclerView) view.findViewById(R.id.food_recyclerview);
reminder=(TextView) view.findViewById(R.id.food_reminder);
subreminder=(TextView) view.findViewById(R.id.food_reminder_sub);
floatingActionButton=(FloatingActionButton)view.findViewById(R.id.add_food);
linearLayoutManager = new LinearLayoutManager(getContext());
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(linearLayoutManager);
loadfoodDB(context);
setFoodAlarms(context);
updateviews(context);
floatingActionButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent=new Intent(getContext(),add_food.class);
intent.putExtra("petname",name);
intent.putExtra("petid",id);
intent.putExtra("petbreed",breed);
intent.putExtra("pettype",type);
getContext().startActivity(intent);
getActivity().finish();
}
});
adapter.updateDataOnNotification(model);
recyclerView.setVisibility(View.VISIBLE);
return view;
}
这种从数据库加载数据的方法
public void loadfoodDB(Context context)
{
food_database db=new food_database(context);
food_db_retrieve foodDbRetrieve=new food_db_retrieve(context);
foodDbRetrieve.openDB();
model=new ArrayList<>();
int newid=Integer.valueOf(id);
c = db.queryData("select * from food_schedule WHERE pet_id ='"+newid+"' ORDER BY food_ID DESC");
try {
if(c != null)
{
if(c.moveToFirst())
{
do{
food_model items=new food_model();
items.setFood_id(c.getInt(0));
items.setPet_id(c.getInt(1));
items.setPet_name(c.getString(2));
items.setType_food(c.getString(3));
items.setDate(c.getString(4));
items.setTime(c.getString(5));
items.setQuantity(c.getString(6));
items.setFood_weight(c.getString(7));
items.setMeal(c.getString(8));
items.setNote(c.getString(9));
items.setSched(c.getString(10));
model.add(items);
}while (c.moveToNext());
}
}
}
catch (Exception e)
{
e.printStackTrace();
}
adapter = new foodRecyclerAdapter(context,model);
recyclerView.setAdapter(adapter);
adapter.notifyDataSetChanged();
foodDbRetrieve.closeDB();
}
你能告诉我为什么它会返回0吗？
答案 0 :(得分：1)
因为你在创建ArrayList之后就显示了toast。
将Toast移至onCreateView()或加载onCreate()
因为在onCreateView()
onCreate()
您的onCreateView()应该是这样的。
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view= inflater.inflate(R.layout.frag_food_sched, container, false);
-------------------
-------------------
loadfoodDB(context);
if(model.size()==0)
{
Toast.makeText(context,"size is "+model.size(),Toast.LENGTH_SHORT).show();
}
else
{
Toast.makeText(context,"size is "+model.size(),Toast.LENGTH_SHORT).show();
}
------------------------
------------------------
return view;
}