I'm trying to use PreferenceFragmentCompat from the v7 support library. When I try to add it, it always returns the following exception
Process: com.sample.preferencetest, PID: 14444
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.sample.preferencetest/com.sample.preferencetest.SettingsActivity}: android.app.Fragment$InstantiationException: Trying to instantiate a class com.sample.preferencetest.SettingsActivity$EmptyFragment that is not a Fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3155)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3263)
at android.app.ActivityThread.access$1000(ActivityThread.java:197)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1687)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6897)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
When I try to use a PreferenceFragment with this, everything works fine. It's only when I try to use the PreferenceFragmentCompat that it fails
The reason I want to use this, is because the onAttach(Activity) method is now deprecated, and earlier devices weren't attaching my interface.
This is the class
package com.sample.preferencetest;
import android.os.Bundle;
//import android.preference.PreferenceFragment; I toggle this to try regular preference fragments.
import android.support.v7.preference.PreferenceFragmentCompat;
import java.util.List;
public class SettingsActivity extends AppCompatPreferenceActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public void onBuildHeaders(List<Header> target) {
loadHeadersFromResource(R.xml.pref_headers, target);
}
protected boolean isValidFragment(String fragmentName) {
return true;
}
public static class EmptyFragment extends PreferenceFragmentCompat {
public EmptyFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public void onCreatePreferences(Bundle bundle, String s) {
}
}
}
Headers XML
<preference-headers xmlns:android="http://schemas.android.com/apk/res/android">
<header
android:fragment="com.sample.preferencetest.SettingsActivity$EmptyFragment"
android:icon="@drawable/ic_info_black_24dp"
android:title="@string/pref_header_general" />
</preference-headers>
Gradle
apply plugin: 'com.android.application'
android {
compileSdkVersion 23
buildToolsVersion "23.0.2"
defaultConfig {
applicationId "com.sample.preferencetest"
minSdkVersion 16
targetSdkVersion 23
versionCode 1
versionName "1.0"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
testCompile 'junit:junit:4.12'
compile 'com.android.support:appcompat-v7:23.2.1'
compile 'com.android.support:design:23.2.1'
compile 'com.android.support:support-v4:23.2.1'
compile 'com.android.support:preference-v7:23.3.0'
}
How am I supposed to use the PreferenceFragmentCompat, if not this way?
This problem occurs, because framework fragments and support fragments are not compatible. If you're using the AppCompatPreferenceActivity
from the samples of the support library, you're using a normal PreferenceActivity
with toolbar support. Support fragments are not supported there. That's why PreferenceFragment
works fine and PreferenceFragmentCompat
doesn't.
If you're only concerned about onAttach(Activity)
being deprecated, don't be. The default implementation of onAttach(Context)
just calls through to it when attached to an activtiy. Therefore it's safe to only implement onAttach(Activity)
to be compatible with all current versions of Android.
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