EditText tooltip error in Android

Question

I am trying to set the prompt as a question mark (?). If I set it as a string in an xml file, I get an error

Error: Resource ID cannot be an empty string (with a "prompt" with the value "?").

<EditText android:id="@+id/txt_to_edit" android:layout_width="92dp" android:layout_height="wrap_content" android:layout_column="8" android:layout_gravity="bottom" android:layout_row="5" android:layout_rowSpan="6" android:hint="?" android:text="@string/txt_label"/> 

If I set a tooltip pointing to @ string / quest in strings.xml, I get the same error. If I try to use! or something like that, it works great. I am using Android SDK 4. Thanks

 <EditText android:id="@+id/txt_to_edit" android:layout_width="92dp" android:layout_height="wrap_content" android:layout_column="8" android:layout_gravity="bottom" android:layout_row="5" android:layout_rowSpan="6" android:hint="@string/quest" android:text="@string/txt_label"/> 

Answer 1

? considered as a special character (e.g. for ?android:attr ). Try \? .

Answer 2

I agree with Amokrane.

Maybe try

 <EditText android:id="@+id/txt_to_edit" android:layout_width="92dp" android:layout_height="wrap_content" android:layout_column="8" android:layout_gravity="bottom" android:layout_row="5" android:layout_rowSpan="6" android:hint="\?" android:text="@string/txt_label"/>