问题描述

我无法让 AlertDialog 将文本传递回调用它的活动.问题似乎是调用 findViewByID 时找不到正确的 EditText，但我是 Android 新手，不知道为什么会这样.

I'm having trouble getting an AlertDialog to pass text back to the activity that calls it. It seems the issue is that it fails to find the proper EditText when calling findViewByID, but I'm new to Android and don't know why that may be.

代码如下:

public class ModifyDialogFragment extends DialogFragment {

/* The activity that creates an instance of this dialog fragment must
 * implement this interface in order to receive event callbacks.
 * Each method passes the DialogFragment in case the host needs to query it. */
public interface MDialogListener {
    public void onMDialogPositiveClick(String newValue);
}

// Use this instance of the interface to deliver action events
MDialogListener mListener;

String mEntryName = "";
EditText mEditText;

@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    // Use the Builder class for convenient dialog construction
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());

    LayoutInflater inflater = getActivity().getLayoutInflater();

    final View modifyView = inflater.inflate(R.layout.modify_dialog, null);

    builder.setView(modifyView);

    final EditText editText = (EditText) getActivity().findViewById(R.id.modificationText);



           builder.setPositiveButton(R.string.modify, new DialogInterface.OnClickListener() {
               public void onClick(DialogInterface dialog, int id) {
                   mListener.onMDialogPositiveClick(editText.getText().toString());
               }
           });
           builder.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
               public void onClick(DialogInterface dialog, int id) {
                   // User cancelled the dialog
               }
           });

    // Create the AlertDialog object and return it
    return builder.create();
}

// Override the Fragment.onAttach() method to instantiate the ModifyDeleteDialogListener
@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    // Verify that the host activity implements the callback interface
    try {
        // Instantiate the MDDialogListener so we can send events to the host
        mListener = (MDialogListener) activity;
    } catch (ClassCastException e) {
        // The activity doesn't implement the interface, throw exception
        throw new ClassCastException(activity.toString()
                + " must implement MDialogListener");
    }
}

以及对应的 modify_dialog.xml:

And the corresponding modify_dialog.xml:

<?xml version="1.0" encoding="utf-8"?>

<EditText xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/modificationText"
    android:inputType="text"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="16dp"
    android:layout_marginLeft="4dp"
    android:layout_marginRight="4dp"
    android:layout_marginBottom="4dp"/>

为什么没有找到editText?我可以做些什么来使这项工作按预期工作，将新字符串传递回活动?

Why isn't the editText being found? What can I do to make this work as intended, passing the new string back to the activity?

推荐答案

改变

final EditText editText = (EditText) getActivity().findViewById(R.id.modificationText);

到

final EditText editText = (EditText) modifyView.findViewById(R.id.modificationText);

您的 EditText 位于 modify_dialog.xml 中，因此您需要使用该 layout 膨胀的变量(此处为 modifyView) 来查找 id 而不是 getActivty() 将查找的 layout.

Your EditText lives in modify_dialog.xml so you need to use the variable that was inflated with that layout (here modifyView) to find the id not the layout that getActivty() will look in.

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