Diálogo de texto de entrada Android

Actualizaré @Aaron update con un enfoque que te dará la oportunidad de estilizar el diálogo de una mejor manera. Aquí está el ejemplo ajustado:

AlertDialog.Builder builder = new AlertDialog.Builder(getContext());
builder.setTitle("Title");
// I'm using fragment here so I'm using getView() to provide ViewGroup
// but you can provide here any other instance of ViewGroup from your Fragment / Activity
View viewInflated = LayoutInflater.from(getContext()).inflate(R.layout.text_inpu_password, (ViewGroup) getView(), false);
// Set up the input
final EditText input = (EditText) viewInflated.findViewById(R.id.input);
// Specify the type of input expected; this, for example, sets the input as a password, and will mask the text
builder.setView(viewInflated);

// Set up the buttons
builder.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        dialog.dismiss();
        m_Text = input.getText().toString();
    }   
}); 
builder.setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        dialog.cancel();
    }   
}); 

builder.show();

Aquí está el ejemplo de layout que se usó para crear el diálogo EditText:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="@dimen/content_padding_normal">

    <android.support.design.widget.TextInputLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <AutoCompleteTextView
            android:id="@+id/input"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="@string/hint_password"
            android:imeOptions="actionDone"
            android:inputType="textPassword" />

    </android.support.design.widget.TextInputLayout>
</FrameLayout>

Aquí puedes encontrar el resultado:

¿Qué tal este EJEMPLO? Parece sencillo.

final EditText txtUrl = new EditText(this);

// Set the default text to a link of the Queen
txtUrl.setHint("http://www.librarising.com/astrology/celebs/images2/QR/queenelizabethii.jpg");

new AlertDialog.Builder(this)
  .setTitle("Moustachify Link")
  .setMessage("Paste in the link of an image to moustachify!")
  .setView(txtUrl)
  .setPositiveButton("Moustachify", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
      String url = txtUrl.getText().toString();
      moustachify(null, url);
    }
  })
  .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
    }
  })
  .show(); 

Me pareció más limpio y más reutilizable extender AlertDialog.Builder para crear una clase de diálogo personalizada. Esto es para un diálogo que le pide al usuario que ingrese un número de teléfono. También se puede proporcionar un número de teléfono preestablecido llamando a setNumber() antes de llamar a show().

InputSenderDialog.java

public class InputSenderDialog extends AlertDialog.Builder {

    public interface InputSenderDialogListener{
        public abstract void onOK(String number);
        public abstract void onCancel(String number);
    }

    private EditText mNumberEdit;

    public InputSenderDialog(Activity activity, final InputSenderDialogListener listener) {
        super( new ContextThemeWrapper(activity, R.style.AppTheme) );

        @SuppressLint("InflateParams") // It's OK to use NULL in an AlertDialog it seems...
        View dialogLayout = LayoutInflater.from(activity).inflate(R.layout.dialog_input_sender_number, null);
        setView(dialogLayout);

        mNumberEdit = dialogLayout.findViewById(R.id.numberEdit);

        setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int id) {
                if( listener != null )
                    listener.onOK(String.valueOf(mNumberEdit.getText()));

            }
        });

        setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int id) {
                if( listener != null )
                    listener.onCancel(String.valueOf(mNumberEdit.getText()));
            }
        });
    }

    public InputSenderDialog setNumber(String number){
        mNumberEdit.setText( number );
        return this;
    }

    @Override
    public AlertDialog show() {
        AlertDialog dialog = super.show();
        Window window = dialog.getWindow();
        if( window != null )
            window.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);
        return dialog;
    }
}

dialog_input_sender_number.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:padding="10dp">

    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        android:paddingBottom="20dp"
        android:text="Input phone number"
        android:textAppearance="@style/TextAppearance.AppCompat.Large" />

    <TextView
        android:id="@+id/numberLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintTop_toBottomOf="@+id/title"
        app:layout_constraintLeft_toLeftOf="parent"
        android:text="Phone number" />

    <EditText
        android:id="@+id/numberEdit"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintTop_toBottomOf="@+id/numberLabel"
        app:layout_constraintLeft_toLeftOf="parent"
        android:inputType="phone" >
        <requestFocus />
    </EditText>

</android.support.constraint.ConstraintLayout>

Uso:

new InputSenderDialog(getActivity(), new InputSenderDialog.InputSenderDialogListener() {
    @Override
    public void onOK(final String number) {
        Log.d(TAG, "The user tapped OK, number is "+number);
    }

    @Override
    public void onCancel(String number) {
        Log.d(TAG, "The user tapped Cancel, number is "+number);
    }
}).setNumber(someNumberVariable).show();