空对象引用上的对话片段'java.lang.String android.content.Context.getPackageName()'

Question

我正在使用DialogFragment并使用Volley将数据插入mysql。数据已成功插入数据库，但之后总是崩溃。我总是在我的logcat java.lang.NullPointerException中得到这个错误：试图在null对象引用上调用虚拟方法"java.lang.String android.content.Context.getPackageName(("错误在我的Toast中。请帮助

public class ExpensesLeisureDialog extends DialogFragment {
EditText name, amount, details;
String nameHolder, amountHolder, detailsHolder;
Boolean CheckEditText;
RequestQueue requestQueue;
HashMap<String,String> hashMap = new HashMap<>();
String finalResult;
HttpParse httpParse = new HttpParse();
String HttpURL = "http://10.0.2.2:63343/TheMoneyger/api/add-leisure.php";
@Override
public Dialog onCreateDialog (Bundle savedInstanceState) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
builder.setView(inflater.inflate(R.layout.fragment_add_expenses_dialog, null));
requestQueue = Volley.newRequestQueue(getActivity().getApplicationContext());
builder.setTitle("Add leisure expense")
.setPositiveButton("Add", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
name = (EditText) getDialog().findViewById(R.id.editText1);
amount = (EditText) getDialog().findViewById(R.id.editText2);
details = (EditText) getDialog().findViewById(R.id.editText3);
CheckEditTextIsEmpty();
StringRequest stringRequest = new StringRequest(Request.Method.POST, HttpURL,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Toast.makeText(getContext(), response, Toast.LENGTH_SHORT).show();
}
},
new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getContext(), error.toString(), Toast.LENGTH_SHORT).show();
}
}) {
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<String, String>();
params.put("expensename", nameHolder);
params.put("expenseamount", amountHolder);
params.put("details", detailsHolder);
return params;
}
};
RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
requestQueue.add(stringRequest);
}
})
.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
return builder.create();
}
public void CheckEditTextIsEmpty() {
nameHolder = name.getText().toString();
amountHolder = amount.getText().toString();
detailsHolder = details.getText().toString();
}

这是我的logcat

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference
             at android.widget.Toast.<init>(Toast.java:114)
             at android.widget.Toast.makeText(Toast.java:277)
             at android.widget.Toast.makeText(Toast.java:267)
             at com.example.merylle.themoneyger.fragment.ExpensesLeisureDialog$2$1.onResponse(ExpensesLeisureDialog.java:65)
             at com.example.merylle.themoneyger.fragment.ExpensesLeisureDialog$2$1.onResponse(ExpensesLeisureDialog.java:62)
             at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:60)
             at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:30)
             at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
             at android.os.Handler.handleCallback(Handler.java:790)
             at android.os.Handler.dispatchMessage(Handler.java:99)
             at android.os.Looper.loop(Looper.java:164)
             at android.app.ActivityThread.main(ActivityThread.java:6494)
             at java.lang.reflect.Method.invoke(Native Method)
             at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
             at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

Answer 1

更新

调用onAttach方法时存储上下文。

public class ExpensesLeisureDialog extends DialogFragment {
Context context;
@Override
public void onAttach(Context context) {
super.onAttach(context);
this.context = context;
}
.
.
}

并在需要时使用上下文变量。

Answer 2

试试这个

• 这是您的代码，您可以在tost-getcontext中传递getcontext((，返回null值

getContext:-它是应用程序/对象的当前状态的上下文。

Toast.makeText(getContext(), response, Toast.LENGTH_SHORT).show();

getContext更改为getActivity，如下所示：

Toast.makeText(getActivity(), response, Toast.LENGTH_SHORT).show();

getActivity:-getActivity是一个函数，它返回一个Activity。它是Fragment的一个函数，返回片段所附加的Activity。如果没有Activity附加到片段，则为null。

我希望它能帮助你