我正在嘗試將信息從我的警報(bào)對(duì)話框傳遞到它所在的父片段。但是，一旦您按下正向按鈕，該應(yīng)用程序就會(huì)崩潰。我真的不知道該怎么辦已經(jīng)閱讀了許多帖子和文章，但找不到問(wèn)題。如果你能幫助我，那就太好了。（我是初學(xué)者）這是我在代碼中的第一個(gè)問(wèn)題和第二個(gè)注釋中得到的錯(cuò)誤。E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.test, PID: 20682 java.lang.NullPointerException: Attempt to invoke interface method 'void com.example.test.SchulfachDialog$SchulfachDialogListener.applyTexts(java.lang.String)' on a null object reference at com.example.test.SchulfachDialog$1.onClick(SchulfachDialog.java:39) at android.support.v7.app.AlertController$ButtonHandler.handleMessage(AlertController.java:167) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5525) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:730) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:620)這是我的警報(bào)對(duì)話框代碼：builder.setView(view) .setTitle("Add new subject") .setMessage("Message") .setNegativeButton("Cancel", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { } }) .setPositiveButton("ok", new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { String name = editTextName.getText().toString(); listener.applyTexts(name); // Problem 1: when positiv Button is pushed this line causes a crash } }); editTextName = view.findViewById(R.id.edit_name); return builder.create();}這是我在片段代碼中覆蓋的應(yīng)用文本：public interface SchulfachDialogListener{ void applyTexts(String name); }}@Override public void applyTexts(String name) { test = name; }}
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溶液：要將數(shù)據(jù)從警報(bào)對(duì)話框傳遞到父片段，更簡(jiǎn)單的方法是讓對(duì)話框擴(kuò)展 DialogFragment。然后使用它們和在它們之間發(fā)送數(shù)據(jù)。setTargetFragmentsetTargetFragment
因?yàn)槟銢](méi)有發(fā)布父片段代碼，所以我假設(shè)這里是你的父片段的xml和java代碼。
主碎屑.java
public class MainFragment extends Fragment implements SchulfachDialogListener{
@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_main, container, false);
Button btnShowAlertDialog = view.findViewById(R.id.button_show_alert_dialog);
btnShowAlertDialog.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SchulfachDialog dialog = new SchulfachDialog();
dialog.setTargetFragment(MainFragment.this, 0);
dialog.show(requireActivity().getSupportFragmentManager(), null);
}
});
return view;
}
@Override
public void applyTexts(String text) {
Toast.makeText(requireActivity(), text, Toast.LENGTH_SHORT).show();
}
}
fragment_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<Button android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Show Alert Dialog"
android:id="@+id/button_show_alert_dialog"/>
</LinearLayout>
讓警報(bào)對(duì)話框擴(kuò)展 DialogFragment。
public class SchulfachDialog extends DialogFragment {
private EditText editTextName;
@NonNull
@Override
public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
AlertDialog.Builder builder = new AlertDialog.Builder(requireActivity());
View view = LayoutInflater.from(requireActivity()).inflate(R.layout.dialog_schulfach, null);
builder.setView(view)
.setTitle("Add new subject")
.setMessage("Message")
.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
}
})
.setPositiveButton("ok", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
String name = editTextName.getText().toString();
SchulfachDialogListener listener = (SchulfachDialogListener) getTargetFragment();
listener.applyTexts(name);
}
});
editTextName = view.findViewById(R.id.edit_name);
return builder.create();
}
}
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