How to support `layout_columnWeight` and `layout_rowWeight` in pre API 21?

For beginners like me @Amir Ziarati's answer is on point. you need to add this line in your build.gradle (Module:app)

implementation 'com.android.support:gridlayout-v7:26.1.0'

Like this

dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'com.android.support:appcompat-v7:26.1.0'
implementation 'com.android.support.constraint:constraint-layout:1.0.2'
implementation 'com.android.support:gridlayout-v7:26.1.0'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.1'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1' 
}

And then use

<android.support.v7.widget.GridLayout>
...</android.support.v7.widget.GridLayout>

the version of GridLayout in support library is backward compatible and supports weights as mentioned here:

https://developer.android.com/reference/android/support/v7/widget/GridLayout.html

so you just need to add compile 'com.android.support:gridlayout-v7:23.1.1' to your build.gradle file and use support gridlayout instead ;)

use it like below (android.support.v7.widget.GridLayout) in your layout xml file:

<android.support.v7.widget.GridLayout
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/container_grid"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:columnCount="2"
    app:rowCount="3"
    app:orientation="horizontal">

    <View
        android:id="@+id/view_red"
        android:layout_height="100dp"
        android:layout_width="100dp"
        app:layout_columnWeight="1"
        app:layout_rowWeight="1"
        app:layout_gravity="center"
        android:background="#ff0000"
        app:layout_row="0"
        app:layout_column="0" />
</android.support.v7.widget.GridLayout>