Following bug occurs on a fairly new Motorola Defy with Android 11:

I have a weird black bottom bar in my app when my targetSdkVersion is 22 which disappears if I set 24 as targetSdkVersion.

The bug does not appear on my Motorola E2 with Android 5.

I'd wish to stay at targetSdkVersion 22 for valid reasons. The app will run on a very low number of known devices at our customer. The phone is locked up in some sort of a kiosk mode. targetSdkVersion 22 doesn't enforce RuntimePermissions which makes is perfect for the use as kiosk app.

Here's the stripped down build.gradle (:app)

apply plugin: 'com.android.application'

android {
    compileSdkVersion 30

    defaultConfig {
        //...
        minSdkVersion 17
        //noinspection ExpiredTargetSdkVersion
        targetSdkVersion 22
        versionCode 140
        versionName "1.4.0 in dev "   new Date().format('yyyy-MM-dd HH:mm:ss')
    }
}

dependencies {

    //We don't plan to switch to AndroidX with our legacy Android apps that were written around API level 19
    //noinspection GradleCompatible
    implementation 'com.android.support:appcompat-v7:28.0.0'
}

Here's the stripped down AndroidManifest.xml:

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

    <application
        android:name="xxxxx.xxxxApplication"
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme">
        <activity
            android:name="xxxxxx.PresetActivity"
            android:configChanges="keyboardHidden|orientation"
            android:label="@string/app_name"
            android:screenOrientation="portrait"
            android:windowSoftInputMode="stateUnchanged" 
            android:launchMode="singleTop">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
       
    </application>
</manifest>

Here's the stripped down styles.xml (I only have one styles.xml):

<resources xmlns:android="http://schemas.android.com/apk/res/android">

     <!-- Application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
    </style>

</resources>

Stripped down activity code:

package xxxxxxxxxxx.ui.activity;

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import xxxxxxxxx.ui.fragment.PresetFragment;
import android.support.v7.app.AppCompatActivity;

public class PresetActivity extends AppCompatActivity { 

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_container);

        // Add fragment the correct way
        // http://stackoverflow.com/questions/8474104/android-fragment-lifecycle-over-orientation-changes

        Fragment fragment = getSupportFragmentManager().findFragmentById(
                R.id.FragmentContainer);

        if (fragment == null) {

            FragmentTransaction fragmentTransaction = getSupportFragmentManager()
                    .beginTransaction();

            fragmentTransaction.add(R.id.FragmentContainer,
                    new PresetFragment());

            fragmentTransaction.commit();
        }
    }
}

activity_container.xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@ id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:animateLayoutChanges="true"
    android:background="@color/color_background"
    android:paddingTop="8dp"
    tools:ignore="MergeRootFrame">

    <fragment
        android:id="@ id/status_bar_fragment"
        
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        tools:layout="@layout/fragment_status_bar" />

    <FrameLayout
        android:id="@ id/FragmentContainer"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@ id/status_bar_fragment"
        android:layout_alignRight="@ id/status_bar_fragment"></FrameLayout>
        
        
</RelativeLayout>

CodePudding user response：

The system assumes that your application cannot handle non standard aspect ratio and uses a 16:9 letterbox.

This can be controlled with resizeableActivity :

<activity
    ....
    android:resizeableActivity="true"

If you don't set it, the default value is true if you target API 24 or greater, and false otherwise.