ConstraintLayout

ConstraintLayout offers more flexibility and better performance for complex layouts

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FF9800"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/bt1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="1"
        android:layout_margin="5dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/bt2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="2"
        android:layout_margin="5dp"
        app:layout_constraintStart_toEndOf="@id/bt1"
        app:layout_constraintTop_toTopOf="@id/bt1" />

    <Button
        android:id="@+id/bt3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="3"
        android:layout_margin="5dp"
        app:layout_constraintStart_toEndOf="@id/bt2"
        app:layout_constraintTop_toTopOf="@id/bt2" />

    <Button
        android:id="@+id/bt4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="4"
        android:layout_margin="5dp"
        app:layout_constraintStart_toEndOf="@id/bt1"
        app:layout_constraintTop_toBottomOf="@id/bt2" />

    <Button
        android:id="@+id/bt5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="5"
        android:layout_margin="5dp"
        app:layout_constraintEnd_toStartOf="@id/bt3"
        app:layout_constraintTop_toBottomOf="@id/bt4" />

    <Button
        android:id="@+id/bt6"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="6"
        android:layout_margin="5dp"
        app:layout_constraintEnd_toStartOf="@id/bt3"
        app:layout_constraintTop_toBottomOf="@id/bt5" />

    <Button
        android:id="@+id/bt7"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="7"
        android:layout_margin="5dp"
        app:layout_constraintTop_toBottomOf="@id/bt6" />

    <Button
        android:id="@+id/bt8"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="8"
        android:layout_margin="5dp"
        app:layout_constraintTop_toBottomOf="@id/bt7"
        app:layout_constraintEnd_toEndOf="parent" />

    <Button
        android:id="@+id/bt9"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="9"
        android:layout_margin="5dp"
        app:layout_constraintTop_toBottomOf="@id/bt8"
        app:layout_constraintEnd_toEndOf="parent" />

    <Button
        android:id="@+id/bt10"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="10"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

    <Button
        android:id="@+id/bt11"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="11"
        android:layout_margin="5dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <Button
        android:id="@+id/bt12"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="12"
        android:layout_margin="5dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

    <Button
        android:id="@+id/bt13"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="13"
        android:layout_margin="5dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

    <Button
        android:id="@+id/bt14"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="14"
        android:layout_margin="5dp"
        app:layout_constraintTop_toBottomOf="@id/bt9"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>