How does one declare the type of an Android preference?

Question

I have a preferences.xml that looks like this:

<?xml version="1.0" encoding="utf-8"?> <PreferenceScreen   xmlns:android="http://schemas.android.com/apk/res/android">  <EditTextPreference   android:name="Sample"   android:enabled="true"   android:persistent="true"   android:summary="Sample"   android:defaultValue="3.0"   android:title="Sample"   android:key="sample" /> </PreferenceScreen> 

When I do sp.getString("sample", "3.0"), it works fine and returns a string, but it shouldn't be a string, it should be a float. Running sp.getFloat("sample", 3.0f) throws a ClassCastException because it is a string.

What should I put in the XML so that the preference is stored as a float?

Answer 1

In your preferences xml you can add an option android:numeric with the value "integer". This way the user should only be able to enter a valid integer value.

When loading the setting you should try to parse it to a number yourself (as all values are stored as Strings (@mbaird below)):

try {   float val = Float.parseFloat(sp.getString("sample", "3.0f")); } catch (NumberFormatException e) {   // "sample" was not an integer value   // You should probably start settings again } 

Answer 2

If you are using the built in preferences screen API instead of writing your own preferences Dialogs or Activities, then you are going to be a bit limited in some respects. For example EditTextPreference will always store the value as a String.

From the API Doc:

This preference will store a string into the SharedPreferences.

I note that there doesn't appear to be any way for you to restrict the user to just typing in a valid floating point number in your text field. What would you do if they typed in "abc"?