AppCompatPreferenceActivity strange padding on left and right in Android 4.4

Question

I have an SettingsActivity extending AppCompatPreferenceActivity.

my pref_headers.xml looks like this:

<preference-headers xmlns:android="http://schemas.android.com/apk/res/android">
    <header
        android:fragment="com.blabla.activities.fragments.ProfileFragment"
        android:icon="@drawable/ic_users"
        android:title="Profil">
    </header>
</preference-headers>

Where the fragment code looks like this:

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public class ProfileFragment extends PreferenceFragment {
    @BindView(R.id.email)
    TextView email;
    @BindView(R.id.username)
    TextView username;
    @BindView(R.id.loadingPanel)
    RelativeLayout loadingPanel;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_profile, container, false);
        ButterKnife.bind(this, rootView);

        if (setActionbarListener != null) {
            setActionbarListener.setActionbarTitle("Profil");
        }

        loadingPanel.setVisibility(View.VISIBLE);
        UsernameHandler uHandler = UsernameHandler.getInstance(new UsernameResult() {
            @Override
            public void finished(String uname) {
                username.setText(uname);
                loadingPanel.setVisibility(View.GONE);  // hide loading spinner
            }
        });
        email.setText(MainActivity.getFbUser().getEmail());

        return rootView;
    }
}

My Problem is, that there is some space on the left and the right side to the layout I am loading. This padding definitely does not come from the layout itself. When starting the app in android 8.1 there is no such padding/margin.

See the picture:

Finally the code of the SettingsActivity:

public class SettingsActivity extends AppCompatPreferenceActivity implements OnSetActionbarTitleListener {

    /**
     * A preference value change listener that updates the preference's summary
     * to reflect its new value.
     */
    private static Preference.OnPreferenceChangeListener sBindPreferenceSummaryToValueListener = new Preference.OnPreferenceChangeListener() {
        @Override
        public boolean onPreferenceChange(Preference preference, Object value) {
            String stringValue = value.toString();

            if (preference instanceof ListPreference) {
                // For list preferences, look up the correct display value in
                // the preference's 'entries' list.
                ListPreference listPreference = (ListPreference) preference;
                int index = listPreference.findIndexOfValue(stringValue);

                // Set the summary to reflect the new value.
                preference.setSummary(
                        index >= 0
                                ? listPreference.getEntries()[index]
                                : null);

            } else if (preference instanceof RingtonePreference) {
                // For ringtone preferences, look up the correct display value
                // using RingtoneManager.
                if (TextUtils.isEmpty(stringValue)) {
                    // Empty values correspond to 'silent' (no ringtone).
                    preference.setSummary(R.string.pref_ringtone_silent);

                } else {
                    Ringtone ringtone = RingtoneManager.getRingtone(
                            preference.getContext(), Uri.parse(stringValue));

                    if (ringtone == null) {
                        // Clear the summary if there was a lookup error.
                        preference.setSummary(null);
                    } else {
                        // Set the summary to reflect the new ringtone display
                        // name.
                        String name = ringtone.getTitle(preference.getContext());
                        preference.setSummary(name);
                    }
                }

            } else {
                // For all other preferences, set the summary to the value's
                // simple string representation.
                preference.setSummary(stringValue);
            }
            return true;
        }
    };

    /**
     * Helper method to determine if the device has an extra-large screen. For
     * example, 10" tablets are extra-large.
     */
    private static boolean isXLargeTablet(Context context) {
        return (context.getResources().getConfiguration().screenLayout
                & Configuration.SCREENLAYOUT_SIZE_MASK) >= Configuration.SCREENLAYOUT_SIZE_XLARGE;
    }

    /**
     * Binds a preference's summary to its value. More specifically, when the
     * preference's value is changed, its summary (line of text below the
     * preference title) is updated to reflect the value. The summary is also
     * immediately updated upon calling this method. The exact display format is
     * dependent on the type of preference.
     *
     * @see #sBindPreferenceSummaryToValueListener
     */
    public static void bindPreferenceSummaryToValue(Preference preference) {
        // Set the listener to watch for value changes.
        preference.setOnPreferenceChangeListener(sBindPreferenceSummaryToValueListener);

        // Trigger the listener immediately with the preference's
        // current value.
        sBindPreferenceSummaryToValueListener.onPreferenceChange(preference,
                PreferenceManager
                        .getDefaultSharedPreferences(preference.getContext())
                        .getString(preference.getKey(), ""));
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setupActionBar();
    }


    /**
     * Set up the {@link android.app.ActionBar}, if the API is available.
     */
    private void setupActionBar() {
        getLayoutInflater().inflate(R.layout.pref_toolbar, (ViewGroup)findViewById(android.R.id.content));
        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        if (toolbar != null) {
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        }

        setActionBarBelowContent();
    }

    private void setActionBarBelowContent() {
        int horizontalMargin = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 2, getResources().getDisplayMetrics());
        int verticalMargin = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 2, getResources().getDisplayMetrics());
        int actionBarHeight = UserInterfaceUtils.getActionBarHeight(MainActivity.context);
        getListView().setPadding(0, actionBarHeight+10, 0, verticalMargin);
    }

    @Override
    public void onHeaderClick(Header header, int position) {
        setActionBarBelowContent();
        super.onHeaderClick(header, position);
    }

    @Override
    public boolean onMenuItemSelected(int featureId, MenuItem item) {
        int id = item.getItemId();
        if (id == android.R.id.home) {
            onBackPressed();
            return true;
        }
        return super.onMenuItemSelected(featureId, item);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean onIsMultiPane() {
        return isXLargeTablet(this);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    public void onBuildHeaders(List<Header> target) {
        loadHeadersFromResource(R.xml.pref_headers, target);
    }

    /**
     * This method stops fragment injection in malicious applications.
     * Make sure to deny any unknown fragments here.
     */
    @Override
    protected boolean isValidFragment(String fragmentName) {
        return PreferenceFragment.class.getName().equals(fragmentName)
                || SettingsFragment.class.getName().equals(fragmentName)
                || FeedbackFragment.class.getName().equals(fragmentName)
                || ProfileFragment.class.getName().equals(fragmentName)
                || AGBFragment.class.getName().equals(fragmentName)
                || PrivacyFragment.class.getName().equals(fragmentName)
                || FAQFragment.class.getName().equals(fragmentName)
                || LicenseFragment.class.getName().equals(fragmentName);
    }

    @Override
    public void onBackPressed() {
        super.onBackPressed();
        setActionbarTitle("Einstellungen");
    }

    @Override
    public void setActionbarTitle(String title) {
        getSupportActionBar().setTitle(title);
    }
}

Edit - added layout

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/item_list_item"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.CardView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:cardUseCompatPadding="true"
        app:cardElevation="4dp"
        app:cardCornerRadius="0dp">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_marginTop="10dp"
            android:padding="15dp"
            android:orientation="vertical">

            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:orientation="horizontal">

                <TextView
                    android:id="@+id/preUsername"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:text="Dein Benutzername:"
                    android:textAppearance="@style/profileText"
                    android:textStyle="bold"/>

                <TextView
                    android:id="@+id/username"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAppearance="@style/profileText"
                    android:layout_marginLeft="5dp"/>

            </LinearLayout>

            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:orientation="horizontal">

                <TextView
                    android:id="@+id/preEmail"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAppearance="@style/profileText"
                    android:textStyle="bold"
                    android:text="Deine Email:"/>

                <TextView
                    android:id="@+id/email"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:textAppearance="@style/profileText"
                    android:layout_marginLeft="5dp"/>

            </LinearLayout>

        </LinearLayout>
    </android.support.v7.widget.CardView>

    <RelativeLayout
        android:id="@+id/loadingPanel"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="center_vertical|center_horizontal"
        android:gravity="center">

        <ProgressBar
            android:id="@+id/progressBar"
            style="@style/MyProgressBarSpinner"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:indeterminate="true" />
    </RelativeLayout>

</RelativeLayout>

Answer 1

This is as per design i.e. expected behavior that you are getting padding on KitKat devices. From Official documentation:

On pre-Lollipop platforms, CardView does not clip the bounds of the Card for the rounded corners. Instead, it adds padding to content so that it won't overlap with the rounded corners. You can disable this behavior by setting this field to false.

Solution:

In XML Layout: app:cardPreventCornerOverlap="false"

OR

In Java: setPreventCornerOverlap(false);

So in your case:

<android.support.v7.widget.CardView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:cardUseCompatPadding="true"
    app:cardElevation="4dp"
    app:cardPreventCornerOverlap="false"
    app:cardCornerRadius="0dp">

Hope it will help you!

Answer 2

You're right that this padding is not because of CardView:

It happens on pre-lolipop because of prefs paddings:

In order to remove this border in your case you just could remove paddings from parent view after view is created

 @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        View containerParent = (View)view.getParent();
        containerParent.setPadding(0, 0, 0, 0);
    }

This will remove paddings on pre-lolipop