[SOLVED] How do I use Android's DropDownPreference?

Issue

I’m trying to build a preference screen with a DropDownPreference. Initially I was using the following in my gradle file compile 'com.android.support:preference-v14:25.3.1' but switched to compile 'com.android.support:preference-v7:25.3.1' when I noticed the DropDownPreference was included in v7, not v14 (I thought v14 might also include everything from v7, but I guess not?). My XML looks like this:

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

<PreferenceScreen
xmlns:android="http://schemas.android.com/apk/res/android"
android:title="@string/pref_title"
android:layout_height="match_parent"
android:layout_width="match_parent">

    <PreferenceCategory
        android:key="pref_video"
        android:title="@string/pref_video_title">

        <android.support.v7.preference.DropDownPreference
            android:key="pref_video_quality"
            android:title="@string/pref_video_quality"
            android:summary="@string/pref_summary_video_quality"
            android:entries="@array/pref_entries_video_quality"
            android:entryValues="@array/pref_entries_video_quality" />

    </PreferenceCategory>

</PreferenceScreen>

I’ve also just tried DropDownPreference as the tag. Nothing seems to work. I always get an Error inflating class DropDownPreference error when I try to go to my preference screen in the app.

Any idea how I can use this DropDownPreference? Thanks!

Edit: Adding error message:

 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.app.int_a.giantbombforandroid/com.app.int_a.giantbombforandroid.main.SettingsActivity}: java.lang.ClassCastException: android.support.v7.preference.DropDownPreference cannot be cast to android.preference.Preference

Edit: SettingsActivity declaration in AndroidManifest.xml

<activity android:name=".main.SettingsActivity"
  android:configChanges="orientation|screenSize"
  android:theme="@style/PreferenceThemeOverlay.v14.Material">
</activity>

Solution

Follow up from my comment. Code is in Kotlin btw 🙂

styles.xml

<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
    ...
    <item name="preferenceTheme">@style/PreferenceThemeOverlay.v14.Material</item>
</style>

activity_settings.xml

<LinearLayout android:orientation="vertical">

    <android.support.v7.widget.Toolbar 
        android:id="@+id/toolbar" />

    <FrameLayout android:id="@+id/frame"/>

</LinearLayout>

prefs.xml has exactly what you have in your question

Settings.kt

class SettingsActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_settings)

        setupActionBar()

        if (savedInstanceState == null)
            supportFragmentManager
                    .beginTransaction()
                    .add(R.id.frame, SettingsFragment.newInstance())
                    .commit()
    }

    private fun setupActionBar() {
        setSupportActionBar(toolbar)
        supportActionBar?.setDisplayHomeAsUpEnabled(true)
    }

    class SettingsFragment : PreferenceFragmentCompat() {

        override fun onActivityCreated(savedInstanceState: Bundle?) {
            super.onActivityCreated(savedInstanceState)

            val actionBar = (activity as AppCompatActivity).supportActionBar

            actionBar?.title = preferenceScreen.title
        }

        override fun onCreatePreferences(bundle: Bundle?, rootKey: String?) {

            // Using this method instead of addPreferencesFromXml so we can specify the root preference screen
            // This way, navigating to a new screen is as simple as calling SettingsFragment.newInstance("new_root")
            setPreferencesFromResource(R.xml.prefs, rootKey)
        }

        companion object {

            fun newInstance(rootKey: String = "root") = SettingsFragment().apply {

                // When you pass a string argument with key ARG_PREFERENCE_ROOT, 
                // PreferenceFragmentCompat picks it up and supplies it as an argument to onCreatePreferences
                arguments = Bundle().apply { putString(ARG_PREFERENCE_ROOT, rootKey) }
            }
        }
    }
}

This is the end result:

enter image description here

Answered By – efemoney

Answer Checked By – Katrina (BugsFixing Volunteer)

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