在ArayAdapter中使用Spinner在空对象引用上调用'java.lang.String java.lang.Object.toString（）'

Question

我正在创建一个Android应用。在其中；

• 创建用户
• 成功完成用户创建后，应用显示了另一项活动

身份验证和帐户创建正常。

我创建的第二个活动有一个微调器。此微调器由多余的nameDoctor中的值填充。

微调器是第一次工作。但是，如果我按“后退”按钮或单击任何其他按钮（该按钮在添加微调器之前曾起作用），应用程序将崩溃，并显示NullPointerException。

由于微调器接收到该值，因此其值应为非null。但是我不确定NPE来自哪里。

如果有人可以帮助我，我是android应用程序开发的新手。

    //code
    private void registerMedecin() {
       //code
        mAuth.createUserWithEmailAndPassword(doctor.email, password).addOnCompleteListener(new 
        OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if (!task.isComplete()) {
                    Toast.makeText(Account.this, "Account creation error: " + 
        task.getException().getMessage(), Toast.LENGTH_LONG).show();
                    Log.e("doctor", "Account creation error: " + task.getException().getMessage());
                } else {

                    Log.e("Adddoctor", "user account created");

                    Intent sendNameIntent = new Intent(Compte.this, rdv_detail.class);
                    String name=nameDoctor.getText().toString();
                    sendNameIntent.putExtra("nameDoctor",name);
                    startActivity(sendNameIntent);
                    new Thread(new Runnable() {
                        @Override
                        public void run() {
                            SaveDoctorData(doctor);




                        }
                    }).start();
                }
            }
        });
    }

rdv_detail.java

    //code
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_rdv_detail);

        spinner_doc =findViewById(R.id.spinner_doctor);

        String nameExtra = getIntent().getStringExtra("nameDoctor");
        ArrayList<String> spinnerData = new ArrayList<String>();
        spinnerData.add(nameExtra);

        ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(rdv_detail.this,
              android.R.layout.simple_spinner_item, spinnerData);

        spinner_doc.setAdapter(arrayAdapter);




}

LOGCAT

    Process: com.example.healthy, PID: 21674
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
        at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:457)
        at android.widget.ArrayAdapter.getView(ArrayAdapter.java:419)
        at android.widget.AbsSpinner.onMeasure(AbsSpinner.java:206)
        at android.widget.Spinner.onMeasure(Spinner.java:614)
        at androidx.appcompat.widget.AppCompatSpinner.onMeasure(AppCompatSpinner.java:428)
        at android.view.View.measure(View.java:24530)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1552)
        at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1204)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:723)
        at android.view.View.measure(View.java:24530)
        at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:735)
        at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:481)
        at android.view.View.measure(View.java:24530)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at androidx.appcompat.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:143)
        at android.view.View.measure(View.java:24530)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
        at androidx.appcompat.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:403)
        at android.view.View.measure(View.java:24530)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
        at android.view.View.measure(View.java:24530)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:6828)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1552)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:842)

Answer 1

由tryng导致将空对象转换为字符串String nameExtra = getIntent().getStringExtra("nameDoctor");

请在将nameExtra传递到数组之前进行检查。

如果不为空，请对此答案发表评论。