background of my activity becomes transparent while closing the app-CodePudding

I've created a calculator app, and it works fine, but there's one question - why the background becomes transparent when i close the app by performing home gesture? Here's how it looks:

how to repair this? Thanks, any help appreciated.

Here's the code for this UI, MDC Android:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp">


    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_gravity="bottom"
        android:layout_weight="1">


        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="130dp"
            android:layout_marginBottom="5dp"
            android:layout_weight="0"
            android:layout_gravity="bottom"
            android:orientation="horizontal"
            >

            <TextView
                android:id="@ id/textViewResult"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="bottom"
                android:layout_marginRight="10dp"
                android:layout_marginBottom="1dp"
                android:layout_weight="2"
                android:text=""
                android:textAlignment="textEnd"
                android:textSize="50sp" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="0"
            android:layout_marginTop="0dp"
            android:orientation="horizontal"/>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_gravity="bottom"
            android:layout_marginBottom="5dp"
            android:orientation="horizontal">

            <Button
                android:id="@ id/buttonDivide"
                android:layout_width="wrap_content"
                android:layout_height="75dp"
                android:layout_marginLeft="5dp"
                android:layout_marginTop="10dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary2"
                android:gravity="center"
                android:text="/"
                android:textAlignment="center"
                android:textColor="@color/md_theme_dark_primary"
                android:textSize="30sp"
                android:textStyle="bold" />

            <Button
                android:id="@ id/buttonMultiply"
                android:layout_width="wrap_content"
                android:layout_height="75dp"
                android:layout_marginLeft="5dp"
                android:layout_marginTop="10dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary2"
                android:gravity="center"
                android:text="*"
                android:textAlignment="center"
                android:textColor="@color/md_theme_dark_primary"
                android:textSize="30sp"
                android:textStyle="bold" />

            <Button
                android:id="@ id/buttonMinus"
                android:layout_width="wrap_content"
                android:layout_height="75dp"
                android:layout_marginLeft="5dp"
                android:layout_marginTop="10dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary2"
                android:gravity="center"
                android:text="-"
                android:textAlignment="center"
                android:textColor="@color/md_theme_dark_primary"
                android:textSize="30sp"
                android:textStyle="bold" />

            <Button
                android:id="@ id/buttonPlus"
                android:layout_width="wrap_content"
                android:layout_height="75dp"
                android:layout_marginLeft="5dp"
                android:layout_marginTop="10dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary2"
                android:gravity="center"
                android:text=" "
                android:textAlignment="center"
                android:textColor="@color/md_theme_dark_primary"
                android:textSize="30sp"
                android:textStyle="bold" />

            <Button
                android:id="@ id/buttonEquality"
                android:layout_width="wrap_content"
                android:layout_height="75dp"
                android:layout_marginLeft="5dp"
                android:layout_marginTop="10dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary2"
                android:gravity="center"
                android:text="="
                android:textAlignment="center"
                android:textColor="@color/md_theme_dark_primary"
                android:textSize="30sp"
                android:textStyle="bold" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="horizontal"
            android:layout_gravity="bottom"
            >

            <Button
                android:id="@ id/button7"
                android:text="7"
                android:layout_marginTop="1dp"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary"
                android:gravity="center"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:padding="8dp" />

            <Button
                android:id="@ id/button8"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginLeft="5dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary"
                android:gravity="center"
                android:text="8"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:layout_marginTop="1dp"
                android:padding="8dp" />

            <Button
                android:id="@ id/button9"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginLeft="5dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary"
                android:gravity="center"
                android:text="9"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:layout_marginTop="1dp"
                android:padding="8dp" />

        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="horizontal"
            android:layout_gravity="bottom">

            <Button
                android:id="@ id/button4"
                android:text="4"
                android:layout_marginTop="1dp"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary"
                android:gravity="center"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:padding="8dp"
                 />

            <Button
                android:id="@ id/button5"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginLeft="5dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary"
                android:gravity="center"
                android:text="5"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:layout_marginTop="1dp"
                android:padding="8dp" />

            <Button
                android:id="@ id/button6"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginLeft="5dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary"
                android:gravity="center"
                android:text="6"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:layout_marginTop="1dp"
                android:padding="8dp" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="horizontal"
            android:layout_gravity="bottom">

            <Button
                android:id="@ id/button1"
                android:text="1"
                android:layout_marginTop="1dp"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary"
                android:gravity="center"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:padding="8dp" />

            <Button
                android:id="@ id/button2"
                android:text="2"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginLeft="5dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary"
                android:gravity="center"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:layout_marginTop="1dp"
                android:padding="8dp" />

            <Button
                android:id="@ id/button3"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginLeft="5dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary"
                android:gravity="center"
                android:text="3"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:layout_marginTop="1dp"
                android:padding="8dp" />
        </LinearLayout>
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:orientation="horizontal"
            android:layout_gravity="bottom"
            android:layout_marginBottom="5dp">

            <Button
                android:id="@ id/buttonPoint"
                android:text="."
                android:layout_marginTop="1dp"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary2"
                android:gravity="center"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:padding="8dp" />

            <Button
                android:id="@ id/button0"
                android:text="0"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginLeft="5dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary"
                android:gravity="center"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:layout_marginTop="1dp"
                android:padding="8dp" />

            <Button
                android:id="@ id/buttonDelete"
                android:layout_width="wrap_content"
                android:layout_height="120dp"
                android:layout_marginLeft="5dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary2"
                android:gravity="center"
                android:text="DEL"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:textColor="@color/md_theme_dark_error"
                android:layout_marginTop="1dp"
                android:padding="8dp" />
        </LinearLayout>
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_marginBottom="60dp"
            android:orientation="horizontal"
            android:layout_gravity="bottom">

            <Button
                android:id="@ id/buttonClear"
                android:layout_width="wrap_content"
                android:layout_height="75dp"
                android:layout_marginLeft="5dp"
                android:layout_marginRight="5dp"
                android:layout_weight="1"
                android:backgroundTint="@color/md_theme_dark_onPrimary2"
                android:gravity="center"
                android:text="CLEAR"
                android:textAlignment="center"
                android:textSize="30sp"
                android:textStyle="bold"
                android:textColor="@color/md_theme_dark_error"
                android:layout_marginTop="1dp"
                android:padding="8dp" />

        </LinearLayout>
    </LinearLayout>
    </LinearLayout>

I tried disabling the night mode of the system, and apparently in white mode the problem doesn't appear. So the dark mode is causing the problem.

CodePudding user response：

If the dark mode from your phone does that, then you can check res->values->themes->themes.xml(night) and set the default background color.

Another fix is to set the background in the LinearLayout. "android:background="#ffffff"" / "android:background="@color/your_color""

Example:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@color/your_color"
android:padding="16dp">


<LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_gravity="bottom"
    android:layout_weight="1">


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="130dp"
        android:layout_marginBottom="5dp"
        android:layout_weight="0"
        android:layout_gravity="bottom"
        android:orientation="horizontal"
        >

        <TextView
            android:id="@ id/textViewResult"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom"
            android:layout_marginRight="10dp"
            android:layout_marginBottom="1dp"
            android:layout_weight="2"
            android:text=""
            android:textAlignment="textEnd"
            android:textSize="50sp" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="0"
        android:layout_marginTop="0dp"
        android:orientation="horizontal"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:layout_gravity="bottom"
        android:layout_marginBottom="5dp"
        android:orientation="horizontal">

        <Button
            android:id="@ id/buttonDivide"
            android:layout_width="wrap_content"
            android:layout_height="75dp"
            android:layout_marginLeft="5dp"
            android:layout_marginTop="10dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary2"
            android:gravity="center"
            android:text="/"
            android:textAlignment="center"
            android:textColor="@color/md_theme_dark_primary"
            android:textSize="30sp"
            android:textStyle="bold" />

        <Button
            android:id="@ id/buttonMultiply"
            android:layout_width="wrap_content"
            android:layout_height="75dp"
            android:layout_marginLeft="5dp"
            android:layout_marginTop="10dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary2"
            android:gravity="center"
            android:text="*"
            android:textAlignment="center"
            android:textColor="@color/md_theme_dark_primary"
            android:textSize="30sp"
            android:textStyle="bold" />

        <Button
            android:id="@ id/buttonMinus"
            android:layout_width="wrap_content"
            android:layout_height="75dp"
            android:layout_marginLeft="5dp"
            android:layout_marginTop="10dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary2"
            android:gravity="center"
            android:text="-"
            android:textAlignment="center"
            android:textColor="@color/md_theme_dark_primary"
            android:textSize="30sp"
            android:textStyle="bold" />

        <Button
            android:id="@ id/buttonPlus"
            android:layout_width="wrap_content"
            android:layout_height="75dp"
            android:layout_marginLeft="5dp"
            android:layout_marginTop="10dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary2"
            android:gravity="center"
            android:text=" "
            android:textAlignment="center"
            android:textColor="@color/md_theme_dark_primary"
            android:textSize="30sp"
            android:textStyle="bold" />

        <Button
            android:id="@ id/buttonEquality"
            android:layout_width="wrap_content"
            android:layout_height="75dp"
            android:layout_marginLeft="5dp"
            android:layout_marginTop="10dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary2"
            android:gravity="center"
            android:text="="
            android:textAlignment="center"
            android:textColor="@color/md_theme_dark_primary"
            android:textSize="30sp"
            android:textStyle="bold" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:orientation="horizontal"
        android:layout_gravity="bottom"
        >

        <Button
            android:id="@ id/button7"
            android:text="7"
            android:layout_marginTop="1dp"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary"
            android:gravity="center"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:padding="8dp" />

        <Button
            android:id="@ id/button8"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary"
            android:gravity="center"
            android:text="8"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:layout_marginTop="1dp"
            android:padding="8dp" />

        <Button
            android:id="@ id/button9"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary"
            android:gravity="center"
            android:text="9"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:layout_marginTop="1dp"
            android:padding="8dp" />

    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:orientation="horizontal"
        android:layout_gravity="bottom">

        <Button
            android:id="@ id/button4"
            android:text="4"
            android:layout_marginTop="1dp"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary"
            android:gravity="center"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:padding="8dp"
             />

        <Button
            android:id="@ id/button5"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary"
            android:gravity="center"
            android:text="5"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:layout_marginTop="1dp"
            android:padding="8dp" />

        <Button
            android:id="@ id/button6"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary"
            android:gravity="center"
            android:text="6"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:layout_marginTop="1dp"
            android:padding="8dp" />
    </LinearLayout>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:orientation="horizontal"
        android:layout_gravity="bottom">

        <Button
            android:id="@ id/button1"
            android:text="1"
            android:layout_marginTop="1dp"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary"
            android:gravity="center"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:padding="8dp" />

        <Button
            android:id="@ id/button2"
            android:text="2"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary"
            android:gravity="center"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:layout_marginTop="1dp"
            android:padding="8dp" />

        <Button
            android:id="@ id/button3"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary"
            android:gravity="center"
            android:text="3"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:layout_marginTop="1dp"
            android:padding="8dp" />
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:orientation="horizontal"
        android:layout_gravity="bottom"
        android:layout_marginBottom="5dp">

        <Button
            android:id="@ id/buttonPoint"
            android:text="."
            android:layout_marginTop="1dp"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary2"
            android:gravity="center"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:padding="8dp" />

        <Button
            android:id="@ id/button0"
            android:text="0"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary"
            android:gravity="center"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:layout_marginTop="1dp"
            android:padding="8dp" />

        <Button
            android:id="@ id/buttonDelete"
            android:layout_width="wrap_content"
            android:layout_height="120dp"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary2"
            android:gravity="center"
            android:text="DEL"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:textColor="@color/md_theme_dark_error"
            android:layout_marginTop="1dp"
            android:padding="8dp" />
    </LinearLayout>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        android:layout_marginBottom="60dp"
        android:orientation="horizontal"
        android:layout_gravity="bottom">

        <Button
            android:id="@ id/buttonClear"
            android:layout_width="wrap_content"
            android:layout_height="75dp"
            android:layout_marginLeft="5dp"
            android:layout_marginRight="5dp"
            android:layout_weight="1"
            android:backgroundTint="@color/md_theme_dark_onPrimary2"
            android:gravity="center"
            android:text="CLEAR"
            android:textAlignment="center"
            android:textSize="30sp"
            android:textStyle="bold"
            android:textColor="@color/md_theme_dark_error"
            android:layout_marginTop="1dp"
            android:padding="8dp" />

    </LinearLayout>
</LinearLayout>
</LinearLayout>