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[英]Passing an _id from one activity to another when ListView item is clicked
[英]Error while passing data from clicked item in listview to another activity
在使用日記列表填充Listview之后,在單擊特定日記時,相應的圖片必須顯示在另一個活動中。
為此,我在意圖中傳遞了單擊項的位置。 但是,應用程序在執行時崩潰
這是歷史片段代碼
public class HistoryFragment extends Fragment
{
ListView lv;
Context context;
public HistoryFragment()
{
//default constructor
}
//The following method will get the context from the activity to which the fragment is attached
@Override
public void onAttach(Context context) {
super.onAttach(context);
this.context=context;
}
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState)
{
final View view = inflater.inflate(R.layout.scrolllist, container, false);
String uid = FirebaseAuth.getInstance().getCurrentUser().getUid();
DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
DatabaseReference uidRef = rootRef.child("image").child(uid);
ValueEventListener valueEventListener = new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
//List<String> cities = new ArrayList<>();
//cities = new ArrayList<>();
final ArrayList<Word> cities = new ArrayList<>();
for(DataSnapshot ds : dataSnapshot.getChildren()) {
String cityName = ds.getKey();
cities.add(new Word(cityName));
}
lv = (ListView)view.findViewById(R.id.list_of_ds);
ContentAdapter arrayAdapter = new ContentAdapter(context,cities);
lv.setAdapter(arrayAdapter);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError)
{
//Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
}
};
uidRef.addListenerForSingleValueEvent(valueEventListener);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener()
{
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
//String diary_name=title.get(position).toString();
Intent myIntent = new Intent(view.getContext(), DiaryViewActivity.class);
myIntent.putExtra("diaryname", lv.getItemAtPosition(position).toString());
startActivity(myIntent);
}
});
return view;
}
}
This is the activity to which intent is passed
//DiaryViewActivity.java
public class DiaryViewActivity extends AppCompatActivity implements IFirebaseLoadDone
{
ViewPager viewPager;
MAdapter adapter;
DatabaseReference diaries;
IFirebaseLoadDone iFirebaseLoadDone;
FirebaseAuth mAuth=FirebaseAuth.getInstance();
//final ArrayList<Word> word = new ArrayList<Word>();
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_diary_view);
Bundle bd = getIntent().getExtras();
String myVal = bd.getString("diaryname");
String currentUser;
currentUser = mAuth.getCurrentUser().getUid();
diaries = FirebaseDatabase.getInstance().getReference().child("image").child(currentUser)
.child(myVal);
iFirebaseLoadDone = this;
loadDairy();
viewPager = (ViewPager)findViewById(R.id.view_pager);
viewPager.setPageTransformer(true,new DepthPageTransformer());
}
private void loadDairy() {
diaries.addListenerForSingleValueEvent(new ValueEventListener() {
List<Display> diaryList = new ArrayList<>();
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot data:dataSnapshot.getChildren()) {
Display d = data.getValue(Display.class);
//word.add(new Word(d.dname));
diaryList.add(d);
}
iFirebaseLoadDone.onFirebaseLoadSuccess(diaryList);
}
@Override
public void onCancelled(DatabaseError databaseError) {
iFirebaseLoadDone.onFirebaseLoadFailed(databaseError.getMessage());
}
});
}
@Override
public void onFirebaseLoadSuccess(List<Display> diaryList) {
adapter = new MAdapter(this,diaryList);
viewPager.setAdapter(adapter);
}
@Override
public void onFirebaseLoadFailed(String message) {
Toast.makeText(this,"error! "+message,Toast.LENGTH_SHORT).show();
}
}
發生以下錯誤 - 嘗試在空對象引用上調用虛擬方法'void android.widget.listview.setonitemclicklistener(android.widget.adapterview $ onitemclicklistener)'
在您調用lv#setOnItemClickListener
,您的ListView(lv)尚未實例化,直到發生對ValueEventListener#onDataChange
的回調。
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