Question

I have been attempting to use an android.preference.DialogPreference inflated from XML, but the documentation seems to be missing some essential bits, and I cannot find a working example anywhere. My XML now looks like this (I tried many permutations but this seems like a reasonable minimum):

<DialogPreference
android:key="funThing" android:title="Fun Thing"
android:dialogLayout="@layout/fun_layout"
android:positiveButtonText="OK"
android:negativeButtonText="Cancel"
/>

My supposition at this point is that it is required to subclass DialogPreference and not to use it directly. For one, I cannot find a way to associate the actual preference value with an element in the dialog itself, which upon reflection is kind of a giveaway. And also, looking at the source to DialogPreference.java seems to confirm it. And I also just noticed that the official documentation refers to it as a “base class”. But at very least, it would be nice to establish a definitive-enough source on the net which would help the next N people figure this out faster than I did.

For the record, the logfile looks like this:

I/ActivityManager(   61): Starting: Intent { cmp=org.jeremy.android/.PreferencesActivity } from pid 2755
W/Resources( 2755): Converting to string: TypedValue{t=0x10/d=0x4b0 a=-1}
W/Resources( 2755): Converting to string: TypedValue{t=0x10/d=0x20 a=-1}
D/AndroidRuntime( 2755): Shutting down VM
W/dalvikvm( 2755): threadid=1: thread exiting with uncaught exception (group=0x40015560)
E/AndroidRuntime( 2755): FATAL EXCEPTION: main
E/AndroidRuntime( 2755): java.lang.RuntimeException: Unable to start activity ComponentInfo{org.jeremy.android/org.jeremy.android.PreferencesActivity}: android.view.InflateException: Binary XML file line #28: Error inflating class java.lang.reflect.Constructor
E/AndroidRuntime( 2755):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
E/AndroidRuntime( 2755):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
E/AndroidRuntime( 2755):    at android.app.ActivityThread.access$1500(ActivityThread.java:117)
E/AndroidRuntime( 2755):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
E/AndroidRuntime( 2755):    at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime( 2755):    at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime( 2755):    at android.app.ActivityThread.main(ActivityThread.java:3683)
E/AndroidRuntime( 2755):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime( 2755):    at java.lang.reflect.Method.invoke(Method.java:507)
E/AndroidRuntime( 2755):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
E/AndroidRuntime( 2755):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
E/AndroidRuntime( 2755):    at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime( 2755): Caused by: android.view.InflateException: Binary XML file line #28: Error inflating class java.lang.reflect.Constructor
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.createItem(GenericInflater.java:397)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.onCreateItem(GenericInflater.java:417)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.createItemFromTag(GenericInflater.java:428)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.rInflate(GenericInflater.java:481)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.rInflate(GenericInflater.java:493)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.inflate(GenericInflater.java:326)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.inflate(GenericInflater.java:263)
E/AndroidRuntime( 2755):    at android.preference.PreferenceManager.inflateFromResource(PreferenceManager.java:251)
E/AndroidRuntime( 2755):    at android.preference.PreferenceActivity.addPreferencesFromResource(PreferenceActivity.java:262)
E/AndroidRuntime( 2755):    at org.jeremy.android.PreferencesActivity.onCreate(PreferencesActivity.java:40)
E/AndroidRuntime( 2755):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
E/AndroidRuntime( 2755):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
E/AndroidRuntime( 2755):    ... 11 more
E/AndroidRuntime( 2755): Caused by: java.lang.InstantiationException: android.preference.DialogPreference
E/AndroidRuntime( 2755):    at java.lang.reflect.Constructor.constructNative(Native Method)
E/AndroidRuntime( 2755):    at java.lang.reflect.Constructor.newInstance(Constructor.java:415)
E/AndroidRuntime( 2755):    at android.preference.GenericInflater.createItem(GenericInflater.java:383)
E/AndroidRuntime( 2755):    ... 22 more
W/ActivityManager(   61):   Force finishing activity org.jeremy.android/.PreferencesActivity
W/ActivityManager(   61):   Force finishing activity org.jeremy.android/.SplashActivity

Answer 1

This one is weird, you need to subclass DialogPreference. The subclass does not need to do anything. So

public class MyDialogPreference extends DialogPreference {

    public MyDialogPreference(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
    }

} 

can be instantiated. While a plane old DialogPreference can not. Very weird, they should be the exact same thing.