How to adjust button size according to screen size in Android Studio

Question

I'm new to android development, and I am making a calculator in android studio. My calculator works fine but there isa problem with its layout I installed it on my tablet and the buttons were very small as I designed them in Android Studio on an emulator, the button size doesn't change, and need help so that the button size increases as the screen size changes.

My calculator design in Android Studio

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent"
    android:background="#ff000000">
    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/clear"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="110dp"
        android:background="@drawable/clear_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/plus_minus"
        android:layout_alignBottom="@+id/clear"
        android:layout_toRightOf="@+id/clear"
        android:layout_toEndOf="@+id/clear"
        android:layout_marginLeft="-11dp"
        android:background="@drawable/pm_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/per"
        android:layout_alignBottom="@+id/plus_minus"
        android:layout_toRightOf="@+id/plus_minus"
        android:layout_toEndOf="@+id/plus_minus"
        android:layout_marginLeft="-11dp"
        android:background="@drawable/per_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/div"
        android:layout_alignTop="@+id/per"
        android:layout_toRightOf="@+id/per"
        android:layout_toEndOf="@+id/per"
        android:layout_marginLeft="-11dp"
        android:background="@drawable/div_btn"
        android:layout_alignParentRight="false" />

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="70dp"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:id="@+id/disp"
        android:layout_above="@+id/plus_minus"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:textColor="@android:color/white"
        android:textSize="32sp"
        android:inputType="none"
        android:textStyle="normal"
        android:gravity="right" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/seven"
        android:layout_below="@+id/clear"
        android:layout_toLeftOf="@+id/plus_minus"
        android:layout_toStartOf="@+id/plus_minus"
        android:layout_marginTop="-10dp"
        android:layout_alignParentTop="false"
        android:layout_alignParentLeft="true"
        android:background="@drawable/seven_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/eight"
        android:layout_alignTop="@+id/seven"
        android:layout_alignLeft="@+id/plus_minus"
        android:layout_alignStart="@+id/plus_minus"
        android:background="@drawable/eight_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/nine"
        android:layout_alignBottom="@+id/seven"
        android:layout_alignLeft="@+id/per"
        android:layout_alignStart="@+id/per"
        android:background="@drawable/nine_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/mul"
        android:layout_alignTop="@+id/nine"
        android:layout_alignLeft="@+id/div"
        android:layout_alignStart="@+id/div"
        android:background="@drawable/mul_btn" />

    <Button
        android:layout_width="103dp"
        android:layout_height="90dp"
        android:id="@+id/four"
        android:layout_below="@+id/seven"
        android:layout_alignRight="@+id/seven"
        android:layout_alignEnd="@+id/seven"
        android:layout_marginTop="-10dp"
        android:layout_alignParentLeft="false"
        android:background="@drawable/four_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/five"
        android:layout_alignBottom="@+id/four"
        android:layout_alignLeft="@+id/eight"
        android:layout_alignStart="@+id/eight"
        android:background="@drawable/five_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/six"
        android:layout_alignTop="@+id/five"
        android:layout_alignLeft="@+id/nine"
        android:layout_alignStart="@+id/nine"
        android:background="@drawable/six_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/sub"
        android:layout_toEndOf="@+id/nine"
        android:layout_alignTop="@+id/six"
        android:layout_alignLeft="@+id/mul"
        android:layout_alignStart="@+id/mul"
        android:background="@drawable/min_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/one"
        android:layout_below="@+id/four"
        android:layout_alignLeft="@+id/four"
        android:layout_alignStart="@+id/four"
        android:layout_marginTop="-10dp"
        android:layout_alignParentLeft="false"
        android:background="@drawable/one_btn" />

    <Button
        android:layout_width="203dp"
        android:layout_height="90dp"
        android:id="@+id/zero"
        android:layout_below="@+id/one"
        android:layout_alignLeft="@+id/one"
        android:layout_alignStart="@+id/one"
        android:layout_marginTop="-10dp"
        android:background="@drawable/zero_btn"
        android:layout_alignParentLeft="true"
        android:layout_marginLeft="-7dp" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/two"
        android:layout_above="@+id/zero"
        android:layout_alignLeft="@+id/five"
        android:layout_alignStart="@+id/five"
        android:background="@drawable/two_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/three"
        android:layout_below="@+id/five"
        android:layout_alignLeft="@+id/six"
        android:layout_alignStart="@+id/six"
        android:layout_marginTop="-10dp"
        android:background="@drawable/three_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/add"
        android:layout_toEndOf="@+id/three"
        android:layout_below="@+id/six"
        android:layout_alignLeft="@+id/sub"
        android:layout_alignStart="@+id/sub"
        android:layout_marginTop="-10dp"
        android:background="@drawable/plus_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/dot"
        android:layout_below="@+id/two"
        android:layout_alignRight="@+id/three"
        android:layout_alignEnd="@+id/three"
        android:layout_marginTop="-10dp"
        android:background="@drawable/dot_btn" />

    <Button
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:id="@+id/equ"
        android:layout_toEndOf="@+id/dot"
        android:layout_below="@+id/three"
        android:layout_alignLeft="@+id/add"
        android:layout_alignStart="@+id/add"
        android:layout_marginTop="-10dp"
        android:background="@drawable/equ_btn" />

</RelativeLayout>

Answer 1

You have to use layout_weight in order to achieve what you want, and that will be used by wrapping each row of buttons inside a LinearLayout and all that LinearLayouts plus the TextView will be wrapped inside one big LinearLayout instead of your RelativeLayout like the following:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/main_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#ff000000"
    android:orientation="vertical"
    android:weightSum="6" >

    <TextView
        android:id="@+id/disp"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:gravity="center"
        android:inputType="none"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:textColor="@android:color/white"
        android:textSize="32sp"
        android:textStyle="normal" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:orientation="horizontal"
        android:weightSum="4" >

        <Button
            android:id="@+id/clear"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@drawable/clear_btn" />

        <!-- then the three remaining buttons -->

        <LinearLayout />

        <!-- then the four remaining rows -->


        <!-- in the last row the "0" button will have layout_weight="2" NOT "1" -->
    </LinearLayout>

</LinearLayout>

UPDATE:

use ImageButtons instead of Buttons for better scalability, and this is how you must use it:

    <ImageButton
            android:id="@+id/clear"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:background="@android:color/transparent"
            android:src="@drawable/clear_btn"
            android:scaleType="fitCenter" />

    <!-- and so for all Buttons -->

Note here we changed:

1- layout_height : from wrap_content to match_parent .

2- background : removing the drawable(clear_btn) and making it transparent.

and we added:

1- src : assigning to it the drawable(clear_btn).

2- scaleType : making it fitCenter to make it scales in all the available area without ruining the Image scalability ratio.

P.S: in case you are want the Button to take all the area weather it is scalable or not, change scaleType from fitCenter to fitXY (may be you will need that for the "0" Button).

Answer 2

If you want to support multiple screens never drag and drop and resize views manually.

You can check both the android:layout_weight attribute and LinearLayout