Setting Activity crashing while launching in android 10 works well in android 28<. How to fix it?

Question

I have an activity which contains settings. After launching SettingsActivity.java its crashing. It works well when tested in physical device i.e, API 19, API23, API26. I'm facing this issue only in API 29. What is the cause for this problem & How to fix it? refer to the code below

SettingActivity.java

package ak.wp.meto.activity;

import android.annotation.SuppressLint;
import android.content.Context;
import android.os.Bundle;
import android.preference.CheckBoxPreference;
import android.preference.Preference;
import android.preference.PreferenceFragment;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import android.view.MenuItem;
import android.widget.Toast;
import java.io.File;

public class SettingsActivity extends AppCompatActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        initView();
        initToolbar();
    }

    private void initView() {
        setContentView(R.layout.activity_settings);

        // replace linear layout by preference screen
        getFragmentManager().beginTransaction().replace(R.id.content, new MyPreferenceFragment()).commit();
    }

    private void initToolbar() {
        Toolbar mToolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(mToolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
        getSupportActionBar().setTitle(getString(R.string.settings));

    }

    @SuppressLint("ValidFragment")
    public class MyPreferenceFragment extends PreferenceFragment {
        @Override
        public void onCreate(final Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            addPreferencesFromResource(R.xml.settings_preference);
            // clears web cache
            final CheckBoxPreference clr_webcache = (CheckBoxPreference) getPreferenceManager().findPreference("perf_cache_clr");
            clr_webcache.setChecked(false);
            clr_webcache.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {

                @Override
                public boolean onPreferenceChange(Preference preference, Object newValue) {
                    Toast.makeText(getApplicationContext(),"Clearing Cache, Please Wait",Toast.LENGTH_SHORT).show();
                    try {
                        trimCache(getActivity());
                    } catch (Exception e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    return true;
                }
            });
        }

        private void trimCache(Context context) {

            try {
                File dir = context.getCacheDir();
                if (dir != null && dir.isDirectory()) {
                    deleteDir(dir);
                }
            } catch (Exception e) {
                // TODO: handle exception
            }

        }

        private boolean deleteDir(File dir) {

            if (dir != null && dir.isDirectory()) {
                String[] children = dir.list();
                for (int i = 0; i < children.length; i++) {
                    boolean success = deleteDir(new File(dir, children[i]));
                    if (!success) {
                        Toast.makeText(getApplicationContext(),"FAILED:Try clearing using device settings",Toast.LENGTH_SHORT).show();
                        return false;
                    }else{
                        Toast.makeText(getApplicationContext(),"SUCCESS: CACHE CLEARED",Toast.LENGTH_SHORT).show();
                    }
                }
            }
            // The directory is now empty so delete it
            return dir.delete();
        }
        //END OF MYPREFERENCE FRAGMENT
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                finish();
                return true;

            default:
                return super.onOptionsItemSelected(item);
        }
    }

    @Override
    public void onBackPressed() {
        finish();
    }
}

This is my activity_settings.xml

activity_settings.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <include
        android:id="@+id/toolbarTop"
        layout="@layout/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <LinearLayout
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/toolbarTop"
        android:orientation="horizontal" />

</RelativeLayout>

This is my setting_preference.xml

<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">

    <CheckBoxPreference
        android:key="perf_notification"
        android:title="@string/pref_notification_title"
        android:summary="@string/pref_notification_summ"
        android:defaultValue="true" />


    <ListPreference
        android:key="pref_font_size"
        android:title="@string/pref_text_title"
        android:dialogTitle="@string/select_size"
        android:entries="@array/text_entries"
        android:entryValues="@array/text_entries"
        android:defaultValue="@string/default_text" />


    <CheckBoxPreference
        android:key="perf_cache_clr"
        android:title="Clear Cache"
        android:summary="Deletes Cache to Load Latest Updates "
        android:defaultValue="false" />

</PreferenceScreen>

Logcat says fatal exception in SettingsActivity.java in line 28 & 36 LOGCAT

2020-10-23 11:24:23.025 19845-19845/? E/AndroidRuntime: FATAL EXCEPTION: main
    Process: ak.wp.meto, PID: 19845
    java.lang.RuntimeException: Unable to start activity ComponentInfo{ak.wp.meto/ak.wp.meto.activity.SettingsActivity}: java.lang.IllegalStateException: Fragment ak.wp.meto.activity.SettingsActivity.MyPreferenceFragment must be a public static class to be  properly recreated from instance state.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3632)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3784)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2270)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at android.os.Looper.loop(Looper.java:237)
        at android.app.ActivityThread.main(ActivityThread.java:8125)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
     Caused by: java.lang.IllegalStateException: Fragment ak.wp.meto.activity.SettingsActivity.MyPreferenceFragment must be a public static class to be  properly recreated from instance state.
        at android.app.BackStackRecord.doAddOp(BackStackRecord.java:429)
        at android.app.BackStackRecord.replace(BackStackRecord.java:470)
        at android.app.BackStackRecord.replace(BackStackRecord.java:462)
        at ak.wp.meto.activity.SettingsActivity.initView(SettingsActivity.java:36)
        at ak.wp.meto.activity.SettingsActivity.onCreate(SettingsActivity.java:28)
        at android.app.Activity.performCreate(Activity.java:7957)
        at android.app.Activity.performCreate(Activity.java:7946)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1307)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3607)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3784) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2270) 
        at android.os.Handler.dispatchMessage(Handler.java:107) 
        at android.os.Looper.loop(Looper.java:237) 
        at android.app.ActivityThread.main(ActivityThread.java:8125) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)

I'm having ERROR in line 36

getFragmentManager().beginTransaction().replace(R.id.content, new MyPreferenceFragment()).commit();

In turn gave ERROR for function initView() line 28

KIndly help me to sort out this issue

In the crash log, it says, "MyPreferenceFragment must be a public static class to be properly recreated from instance state". What happens if you do it? — Md. Tahmid Mozaffar, Oct 23 '20 at 06:16
Duplicate of https://stackoverflow.com/questions/39295458/fragment-must-be-a-public-static-class-to-be-properly-recreated-from-instance-st — Róbert Nagy, Oct 23 '20 at 06:26
I'm getting Non-static method for Toast.makeText(getApplicationContext().. — abhilash kaveriappa, Oct 23 '20 at 06:26
I made MyPreferenceFragment static it worked after removing Toast.makeText — abhilash kaveriappa, Oct 23 '20 at 06:47

score 0 · Answer 1 · answered Oct 23 '20 at 06:28

You must make an instance of SettingsFragment to launch it

public static MyPreferenceFragment getInstance() {
    MyPreferenceFragment fragment = new MyPreferenceFragment();
    Bundle bundle = new Bundle();
    fragment.setArguments(bundle);
    return fragment;
}

And replace it by calling

getFragmentManager().beginTransaction().replace(R.id.content, MyPreferenceFragment.getInstance()).commit();

score 0 · Answer 2 · answered Oct 23 '20 at 06:35

Put the Fragment into a separate file named just like the Fragment (MyPreferenceFragment.java). It should solve the issue.

Also checkout the new Preference library. Android.preference is being deprecated. Instead of:

import android.preference.CheckBoxPreference;
import android.preference.Preference;
import android.preference.PreferenceFragment;

use :

import androidx.fragment.app.Fragment
import androidx.preference.CheckBoxPreference
import androidx.preference.Preference
import androidx.preference.PreferenceFragmentCompat

score 0 · Accepted Answer · answered Oct 23 '20 at 07:52

BINGO, I solved it!!! Finally, this worked for me: I made MyPreferenceFragment to static class

public static class MyPreferenceFragment extends PreferenceFragment

The second problem was Toast.makeText giving out ERROR saying to make MyPreferenceFragment not static. So I replaced Toast by

Toast.makeText(getActivity().getApplicationContext(),"Clearing Cache, Please Wait",Toast.LENGTH_SHORT).show();

Thank You guys for your support.

Setting Activity crashing while launching in android 10 works well in android 28<. How to fix it?

3 Answers3