Android UI Layouts

Android provides various layouts to help developers design the UI for their applications. These layouts determine how child views are positioned and oriented on the screen. Here's an overview of some of the main UI layouts in Android:

LinearLayout:
- Arranges views in a single direction, either horizontally or vertically.
- Uses android:orientation to specify the direction.
- Views can be weighted to distribute space in a specific ratio.
RelativeLayout:
- Positions views based on their relation to other views or parent boundaries.
- Utilizes attributes like android:layout_below, android:layout_toRightOf, etc., to describe relationships.
FrameLayout:
- Stacks views on top of each other.
- Usually used to display a single view or overlay multiple views.
- Child views are pinned to the top left corner by default, but you can use gravity to adjust the positioning.
TableLayout:
- Organizes views in rows and columns, much like an HTML table.
- Child views are added to TableRow elements, defining the content for each row.
- Columns can be made to shrink or stretch to fit their content.
GridLayout:
- A more powerful and flexible version of TableLayout.
- Organizes views in a grid of rows and columns, but with more control over how items span and fill spaces.
ConstraintLayout:
- A very flexible layout introduced to create complex layouts in a more performant and flat manner.
- Allows you to create constraints between views, ensuring they are positioned relative to one another without the need for nested layouts.
- It has a powerful design editor in Android Studio, making it easier to create responsive layouts.
CoordinatorLayout:
- A super-powered FrameLayout.
- Meant for coordinating the movement of child views within.
- Often used with AppBarLayout and other Design library components for effects like the collapsing toolbar.
ScrollView & HorizontalScrollView:
- Not layouts in the traditional sense but are containers that can be used to wrap other layouts or views, providing them with the capability to scroll.
- ScrollView allows vertical scrolling, while HorizontalScrollView allows horizontal scrolling.
PercentFrameLayout & PercentRelativeLayout:
- Variants of FrameLayout and RelativeLayout from the percent support library, which allow you to set sizes and margins using a percentage of the parent's size.
ViewStub:

A lightweight view with no dimension, used for lazily inflating layouts. Once inflated, it replaces itself with the specified layout, making it useful for conditionally displaying views with minimal initial overhead.

Each of these layouts serves specific needs. Depending on the complexity and requirements of your UI, you might use a combination of these layouts. Also, always strive to keep your layout hierarchies as flat as possible for performance reasons. This can often be achieved with thoughtful design and the use of layouts like ConstraintLayout.

RelativeLayout in Android examples:

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello, RelativeLayout!"
        android:layout_centerInParent="true"/>

</RelativeLayout>

TableLayout examples in Android:

<TableLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TableRow>
        <TextView
            android:text="Row 1, Column 1"/>
        <TextView
            android:text="Row 1, Column 2"/>
    </TableRow>

    <TableRow>
        <TextView
            android:text="Row 2, Column 1"/>
        <TextView
            android:text="Row 2, Column 2"/>
    </TableRow>

</TableLayout>

Nested layouts in Android UI design:

Nesting layouts allows for complex and structured UI designs.
Example of nesting LinearLayout inside RelativeLayout:

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:layout_centerInParent="true">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Nested LinearLayout Example"/>

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Click me"/>

    </LinearLayout>

</RelativeLayout>