我创建了两种删除帖子和编辑帖子的方法。我能够成功执行这两项工作。所有帖子都可以删除。我创建了一个编辑按钮，将用户带到撰写写作后的文本编辑活动（清理）中，同时将要编辑的任务的所有信息都检索到文本编辑框中。所有编辑也都完成了成功。仅当用户尝试删除编辑的任务后，才会出现此问题。该应用程序直接崩溃，并说了一些put-extra方法，该方法将正在编辑的帖子的键发送到另一个类，以填充编辑文本框。用户未编辑并仅添加的帖子将被删除，没有任何问题。它只是被编辑的帖子使应用程序崩溃，即使这些帖子即使在崩溃后也会从firebase数据库中删除...
我希望我的问题有道理 下面是我的代码
public class MyPosts extends AppCompatActivity {
private static final String TAG = "MyPosts";
Toolbar toolbar;
DatabaseReference WorkingData;
DatabaseReference WorkingDataForDeletion;
DatabaseReference tasks;
private BottomNavigationView navigationView;
RecyclerView recyclerView;
ArrayList<WorkInformation> workList;
private AppCompatButton deletePost;
private AppCompatButton editPost;
String currentUserID, postKey;
private FirebaseAuth firebaseAuth;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my_posts);
toolbar = (Toolbar) findViewById(R.id.my_post_toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("My Posts");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
navigationView = findViewById(R.id.bottomNavigationView);
firebaseAuth = FirebaseAuth.getInstance();
currentUserID = firebaseAuth.getCurrentUser().getUid();
WorkingData = FirebaseDatabase.getInstance().getReference().child("UserIndividualTasks");
WorkingData.keepSynced(true);
recyclerView = findViewById(R.id.my_post_recycler_view);
recyclerView.setHasFixedSize(true);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
linearLayoutManager.setReverseLayout(true);
linearLayoutManager.setStackFromEnd(true);
recyclerView.setLayoutManager(linearLayoutManager);
deletePost = findViewById(R.id.myPostDelete);
editPost = findViewById(R.id.myPostEdit);
}
@Override
protected void onStart() {
super.onStart();
}
@Override
protected void onResume() {
super.onResume();
Query query = WorkingData.child(FirebaseAuth.getInstance().getCurrentUser().getUid());
FirebaseRecyclerOptions<WorkInformation> options = new FirebaseRecyclerOptions.Builder<WorkInformation>()
.setQuery(query, WorkInformation.class)
.build();
final FirebaseRecyclerAdapter<WorkInformation, MyViewHolder> adapter = new FirebaseRecyclerAdapter<WorkInformation, MyViewHolder>(options) {
@Override
protected void onBindViewHolder(@NonNull final MyViewHolder holder, int position, @NonNull final WorkInformation model) {
holder.title.setText(model.getWorkTitle());
holder.date.setText(model.getWorkDueDate());
Picasso.get().load(model.getImg()).into(holder.imageView);
holder.deleteBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
postKey = getRef(holder.getAdapterPosition()).getKey();
deleteUserPost();
}
});
holder.editBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
postKey = getRef(holder.getAdapterPosition()).getKey();
Intent goToCleaningForEditPost = new Intent(MyPosts.this, Cleaning.class);
Bundle bundle = new Bundle();
bundle.putString("PostKey", postKey);
goToCleaningForEditPost.putExtras(bundle);
startActivity(goToCleaningForEditPost);
}
});
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.my_posts_individual_row_layout, parent, false);
MyViewHolder viewHolder = new MyViewHolder(view);
return viewHolder;
}
};
recyclerView.setAdapter(adapter);
adapter.startListening();
}
public static class MyViewHolder extends RecyclerView.ViewHolder {
public AppCompatTextView title;
public AppCompatTextView date;
public CircleImageView imageView;
public AppCompatButton deleteBtn;
public AppCompatButton editBtn;
public ConstraintLayout constraintLayout;
public MyViewHolder(View itemView) {
super(itemView);
title = itemView.findViewById(R.id.my_posts_title);
date = itemView.findViewById(R.id.myPostDate);
imageView = itemView.findViewById(R.id.UserImage);
deleteBtn = itemView.findViewById(R.id.myPostDelete);
editBtn = itemView.findViewById(R.id.myPostEdit);
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
switch (id) {
case android.R.id.home:
startActivity(new Intent(MyPosts.this, Services.class));
break;
}
return super.onOptionsItemSelected(item);
}
private void deleteUserPost() {
WorkingDataForDeletion = FirebaseDatabase.getInstance().getReference().child("UserIndividualTasks")
.child(currentUserID)
.child(postKey);
WorkingDataForDeletion.removeValue();
tasks = FirebaseDatabase.getInstance().getReference().child("Tasks").child(postKey);
tasks.removeValue();
}
}
这是Iam现在发送用于编辑帖子的键的课程
public class Cleaning extends AppCompatActivity implements DatePickerDialog.OnDateSetListener {
private static final String TAG = "Cleaning";
private BottomNavigationView navigationView;
DatabaseReference UsersRef, WorkingData, userIndividualPostHistory;
public static final int ERROR_DIALOG_REQUEST = 9001;
ConstraintLayout constraintLayout;
Toolbar toolbar;
AppCompatEditText title;
AppCompatEditText description;
ElegantNumberButton budget;
AppCompatTextView total;
AppCompatEditText date;
private String currentUserID, image, userNameForPost, saveDateForTask, saveTimeForTask, postRandomName, PostKey;
AppCompatEditText places;
private FirebaseAuth firebaseAuth;
AppCompatButton continueservices;
ElegantNumberButton WorkForce;
private final static int MY_PERMISSION_FINE_LOCATION = 101;
private final static int PLACE_PICKER_REQUEST = 1;
double finalBudget, finalBudget2;
private ProgressDialog loadingBar;
private DatabaseReference WorkingDataForEdit, WorkingDataForPostEdit;
Bundle bundle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_cleaning);
toolbar = findViewById(R.id.CleaningToolBar);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("Cleaning service");
navigationView = findViewById(R.id.bottomNavigationView);
navigationView.setSelectedItemId(R.id.Services);
firebaseAuth = FirebaseAuth.getInstance();
currentUserID = firebaseAuth.getCurrentUser().getUid();
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
constraintLayout = findViewById(R.id.cleaningConstraintLayout);
UsersRef = FirebaseDatabase.getInstance().getReference().child("Users");
WorkingData = FirebaseDatabase.getInstance().getReference("Tasks");
userIndividualPostHistory = FirebaseDatabase.getInstance().getReference("UserIndividualTasks");
loadingBar = new ProgressDialog(this);
title = findViewById(R.id.TaskTitle);
description = findViewById(R.id.TaskDescription);
budget = findViewById(R.id.TaskBudget);
total = findViewById(R.id.tasktotal);
date = findViewById(R.id.datepickerr);
date.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
DialogFragment datepicker = new DatePickerFragment();
datepicker.show(getSupportFragmentManager(), "Select Date");
}
});
requestPermission();
places = findViewById(R.id.locationPicker);
places.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
PlacePicker.IntentBuilder builder = new PlacePicker.IntentBuilder();
try {
Log.d(TAG, "onClick: asking permission 3");
Intent intent = builder.build(Cleaning.this);
Log.d(TAG, "onClick: asking permission 4");
startActivityForResult(intent, PLACE_PICKER_REQUEST);
} catch (GooglePlayServicesRepairableException e) {
e.printStackTrace();
} catch (GooglePlayServicesNotAvailableException e) {
e.printStackTrace();
}
}
});
UsersRef.child(currentUserID).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()) {
if (dataSnapshot.hasChild("profileimage")) {
image = dataSnapshot.child("profileimage").getValue().toString();
userNameForPost = dataSnapshot.child("First Name").getValue().toString();
} else {
Toast.makeText(Cleaning.this, "Profile name do not exists...", Toast.LENGTH_SHORT).show();
}
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
continueservices = findViewById(R.id.ContinueServicesButton);
continueservices.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (PostKey != null) {
editIfAlreadyExist();
bundle = null;
} else {
addWorkingTask();
}
}
});
WorkForce = findViewById(R.id.workforce);
WorkForce.setOnClickListener(new ElegantNumberButton.OnClickListener() {
@Override
public void onClick(View view) {
finalBudget = Double.parseDouble(WorkForce.getNumber());
finalBudget2 = Double.parseDouble(budget.getNumber());
finalBudget = finalBudget * finalBudget2;
total.setText(String.valueOf(finalBudget) + " BD ");
}
});
budget.setOnClickListener(new ElegantNumberButton.OnClickListener() {
@Override
public void onClick(View view) {
finalBudget2 = Double.parseDouble(budget.getNumber());
finalBudget = Double.parseDouble(WorkForce.getNumber());
finalBudget2 = finalBudget2 * finalBudget;
total.setText(String.valueOf(finalBudget2) + " BD ");
}
});
navigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
int id = item.getItemId();
switch (id) {
case R.id.Services:
break;
case R.id.Search:
startActivity(new Intent(Cleaning.this, Search.class));
break;
case R.id.Task:
break;
case R.id.Message:
break;
case R.id.Settings:
startActivity(new Intent(Cleaning.this, UserProfile.class));
break;
}
return false;
}
});
bundle = getIntent().getExtras();
if (bundle != null) {
PostKey = bundle.get("PostKey").toString();
WorkingDataForEdit = FirebaseDatabase.getInstance().getReference().child("UserIndividualTasks").child(currentUserID).child(PostKey);
WorkingDataForPostEdit = FirebaseDatabase.getInstance().getReference().child("Tasks").child(PostKey);
}
if (PostKey != null) {
WorkingDataForEdit.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
//Error occurred here line @239
String mtitle = dataSnapshot.child("workTitle").getValue().toString();
String mdescription =
dataSnapshot.child("workDescription").getValue().toString();
String mdate =
dataSnapshot.child("workDueDate").getValue().toString();
String mlocation =
dataSnapshot.child("workLocation").getValue().toString();
String mMen =
dataSnapshot.child("workForce").getValue().toString();
String mbudget =
dataSnapshot.child("workBudget").getValue().toString();
String mtotal =
dataSnapshot.child("total").getValue().toString();
title.setText(mtitle);
description.setText(mdescription);
date.setText(mdate);
places.setText(mlocation);
WorkForce.setNumber(mMen);
budget.setNumber(mbudget);
total.setText(mtotal);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
}
private void editIfAlreadyExist() {
WorkingDataForEdit.child("workTitle").setValue(title.getText().toString());
WorkingDataForEdit.child("workDescription").setValue(description.getText().toString());
WorkingDataForEdit.child("workDueDate").setValue(date.getText().toString());
WorkingDataForEdit.child("workLocation").setValue(places.getText().toString());
WorkingDataForEdit.child("workForce").setValue(WorkForce.getNumber());
WorkingDataForEdit.child("workBudget").setValue(budget.getNumber());
WorkingDataForEdit.child("total").setValue(total.getText().toString());
WorkingDataForPostEdit.child("workTitle").setValue(title.getText().toString());
WorkingDataForPostEdit.child("workDescription").setValue(description.getText().toString());
WorkingDataForPostEdit.child("workDueDate").setValue(date.getText().toString());
WorkingDataForPostEdit.child("workLocation").setValue(places.getText().toString());
WorkingDataForPostEdit.child("workForce").setValue(WorkForce.getNumber());
WorkingDataForPostEdit.child("workBudget").setValue(budget.getNumber());
WorkingDataForPostEdit.child("total").setValue(total.getText().toString());
startActivity(new Intent(Cleaning.this, Search.class));
}
private void requestPermission() {
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
requestPermissions(new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, MY_PERMISSION_FINE_LOCATION);
}
}
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
switch (requestCode) {
case MY_PERMISSION_FINE_LOCATION:
if (grantResults[0] != PackageManager.PERMISSION_GRANTED) {
Toast.makeText(getApplicationContext(), "This app requires location permissions to be granted", Toast.LENGTH_LONG).show();
finish();
}
break;
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
Log.d(TAG, "onActivityResult: asking permission 2");
if (requestCode == PLACE_PICKER_REQUEST) {
if (resultCode == RESULT_OK) {
Place place = PlacePicker.getPlace(Cleaning.this, data);
places.setText(place.getName() + " " + place.getAddress());
}
}
}
private void addWorkingTask() {
loadingBar.setMessage("Posting task.Please Wait....");
loadingBar.show();
loadingBar.setCanceledOnTouchOutside(true);
Calendar callForTime = Calendar.getInstance();
SimpleDateFormat currentTime = new SimpleDateFormat("HH:mm:ss");
saveTimeForTask = currentTime.format(callForTime.getTime());
Date d = new Date();
SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy, HH:mm");
String currentDateandTime = sdf.format(d);
String taskTitle = title.getText().toString();
String taskDescription = description.getText().toString();
String date = this.date.getText().toString();
String location = places.getText().toString();
String workMen = WorkForce.getNumber();
String budget = this.budget.getNumber();
String total = this.total.getText().toString();
if (!TextUtils.isEmpty(taskTitle)) {
if (!TextUtils.isEmpty(taskDescription)) {
if (!TextUtils.isEmpty(date)) {
if (!TextUtils.isEmpty(location)) {
String id = WorkingData.push().getKey();
WorkInformation workInformation = new WorkInformation(id, taskTitle, taskDescription
, date, location, workMen
, budget
, total, image
, currentUserID
, userNameForPost, currentDateandTime, saveTimeForTask);
WorkingData.child(id).setValue(workInformation);
userIndividualPostHistory.child(currentUserID).child(id).setValue(workInformation);
Toast.makeText(this, "Work Information saved", Toast.LENGTH_SHORT).show();
loadingBar.dismiss();
startActivity(new Intent(Cleaning.this, Search.class));
} else {
Toast.makeText(this, "Something is missing", Toast.LENGTH_SHORT).show();
loadingBar.dismiss();
}
}
}
}
}
@Override
public void onDateSet(DatePicker view, int year, int month, int dayOfMonth) {
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.YEAR, year);
calendar.set(Calendar.MONTH, month);
calendar.set(Calendar.DAY_OF_MONTH, dayOfMonth);
String currentDateString = DateFormat.getDateInstance(DateFormat.FULL).format(calendar.getTime());
date.setText(currentDateString);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
switch (id) {
case android.R.id.home:
finish();
break;
}
return super.onOptionsItemSelected(item);
}
}
错误：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.saqib.smarttaskk, PID: 13977
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at com.example.saqib.smarttaskk.Cleaning$8.onDataChange(Cleaning.java:239)
at com.google.firebase.database.obfuscated.zzap.zza(com.google.firebase:firebase-database@@16.0.2:75)
at com.google.firebase.database.obfuscated.zzca.zza(com.google.firebase:firebase-database@@16.0.2:63)
at com.google.firebase.database.obfuscated.zzcd$1.run(com.google.firebase:firebase-database@@16.0.2:55)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6938)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
应用程序终止。
答案 0 :(得分：0)
发生错误是因为没有这样的子workTitle，或者如果它存在，则说明Firebase数据库中该节点下没有数据。建议您检查值是否不为空。
Object title = dataSnapshot.child("workTitle").getValue();
if(title != null)
{
String mtitle = title.toString();
}