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android - 触发按钮时出现白屏

问题描述

为什么每次触发按钮都会使我的屏幕变白。但是这些值正在被删除。这是我的代码，它会引发错误。

final String uniqueKey = requestFormArrayList.get(position).getRequestid();
        final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("ResearchRequest").child(uniqueKey);
        databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                    String termsAgreement = snapshot.child("requestStatus").getValue(String.class);
                            if(termsAgreement.equals("accepted")){
                                holder.acceptresearch_request.setText("accepted");
                                holder.acceptresearch_request.setEnabled(false);
                                holder.deleteresearch_request.setEnabled(false);
                                holder.publishresearch_request.setEnabled(true);
                            }
                            else if (termsAgreement.equals("published")){
                                holder.acceptresearch_request.setEnabled(false);
                                holder.deleteresearch_request.setEnabled(false);
                                holder.publishresearch_request.setText("published");
                                holder.publishresearch_request.setEnabled(false);
                            }
                            else{
                                holder.acceptresearch_request.setEnabled(true);
                                holder.deleteresearch_request.setEnabled(true);
                                holder.publishresearch_request.setEnabled(false);
                            }
            }

上面的代码使按钮启用/禁用取决于条件值。但是每次我删除或触发删除按钮时，它都会将屏幕变为白色并返回 MainActivity，但它会毫无问题地删除数据，只是它变成白色而不是烘烤，这是我的代码。

holder.deleteresearch_request.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                AlertDialog.Builder alert = new AlertDialog.Builder(context);
                alert.setTitle("Delete Research Record");
                alert.setMessage("Are you sure you want to delete");

                alert.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        final String uniqueKey = requestFormArrayList.get(position).getRequestid();
                        final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference("ResearchRequest").child(uniqueKey);
                        databaseReference.removeValue().addOnCompleteListener(new OnCompleteListener<Void>() {
                            @Override
                            public void onComplete(@NonNull Task<Void> task) {
                                if (!task.isSuccessful()) {
                                    Log.i("firebase", "Throwing exception");
                                    throw new RuntimeException(task.getException());
                                }
                                else {
                                    Toast.makeText(context, "Research has been deleted", Toast.LENGTH_SHORT).show();
                                }
                            }
                        });

                    }
                });
                alert.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        Toast.makeText(context, "Cancelled", Toast.LENGTH_SHORT).show();
                        dialog.dismiss();
                    }
                });
                alert.show();
            }
        });

编辑：这是向我抛出的错误，我在这里搜索了 NullPointerException。但我不太关注

2021-01-07 16:37:28.706 25163-25163/? E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.citeresearchrepository, PID: 25163
    java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
        at com.example.citeresearchrepository.AdminAdapter.AdminRequestFormAdapter$1.onDataChange(AdminRequestFormAdapter.java:60)
        at com.google.firebase.database.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:75)
        at com.google.firebase.database.core.view.DataEvent.fire(DataEvent.java:63)
        at com.google.firebase.database.core.view.EventRaiser$1.run(EventRaiser.java:55)
        at android.os.Handler.handleCallback(Handler.java:900)
        at android.os.Handler.dispatchMessage(Handler.java:103)
        at android.os.Looper.loop(Looper.java:219)
        at android.app.ActivityThread.main(ActivityThread.java:8347)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:513)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1055)

我应该在 termsAgreement.isEmpty() 的位置添加另一个条件吗？我认为它符合上述条件，因为当您删除它时，没有 termsAgreement.equals("deleted"); 在数据库中，任何想法解决这个问题？

标签： androidfirebase-realtime-databaseandroid-alertdialogandroid-button

解决方案

String termsAgreement = snapshot.child("requestStatus").getValue(String.class);
                        if(termsAgreement.equals("accepted")){
                            holder.acceptresearch_request.setText("accepted");
                            holder.acceptresearch_request.setEnabled(false);
                            holder.deleteresearch_request.setEnabled(false);
                            holder.publishresearch_request.setEnabled(true);
                        }
                        else if (termsAgreement.equals("published")){
                            holder.acceptresearch_request.setEnabled(false);
                            holder.deleteresearch_request.setEnabled(false);
                            holder.publishresearch_request.setText("published");
                            holder.publishresearch_request.setEnabled(false);
                        }
                        else{
                            holder.acceptresearch_request.setEnabled(true);
                            holder.deleteresearch_request.setEnabled(true);
                            holder.publishresearch_request.setEnabled(false);
                        }

在这里，你的termsAgreement为空。看看你写的第一行String.class。字符串是数据类型。那么，你是怎么称呼它的呢？我认为这就是你得到错误的原因。也许，你真的想写string.class。在.getValue(String.class)你无法调用值。这就是你得到错误的原因。

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