Java
More powerful than LinearLayout and RelativeLayout which use java expression in layout params

FlexLayout

The idea is simple, use java expressions in layout params like layout_left="view1.right+10dp". It is helpful when LinearLayout and RelativeLayout is not enough for you.

<TextView
    app:layout_left="icon.right+10dp"
    app:layout_right="100%-14dp"
    app:layout_centerY="icon.centerY"
    android:layout_height="wrap_content"
    .../>

Try the sample apk: FlexLayout.apk

Adding to project

Add dependencies in your build.gradle:

    dependencies {
        compile 'com.github.mmin18:flexlayout:1.2.0'
    }

Or if you are using Eclipse, just copy FlexLayout.java and attrs.xml to your project.

Layout Params

Remember the app:layout_width is different from android:layout_width
xmlns:app="http://schemas.android.com/apk/res-auto"

% Percentage

<Button
    app:layout_left="10%"
    app:layout_right="10%"
    app:centerY="50%"
    android:layout_height="wrap_content"
    ../>

or

<Button
    app:layout_width="80%"
    app:centerX="50%"
    app:centerY="50%"
    android:layout_height="wrap_content"
    ../>

Reference other views

Reference previous view using prev, next view using next (Position in the XML layout file)

<View ../>        // prev = Previous view in xml layout file

<View
    app:layout_left="prev.right"
    app:layout_right="next.left"
    app:layout_top="prev.top"
    app:layout_bottom="next.bottom" />

<View ../>        // next = Next view in xml layout file

Reference a specific view using view's id

<View
    app:layout_left="view1.right"
    app:layout_right="android:text1.left"
    app:layout_top="view1.top"
    app:layout_bottom="android:text1.bottom" />

<View android:id="@+id/view1"
    ../>
<View android:id="@android:id/text1"
    ../>

You can also use parent to reference the FlexLayout and this to reference the child view itself. Use screen to reference screen size.

(screen, parent, this only support width and height property.)

view.visible: view.getVisibility() == View.VISIBLE

view.gone: view.getVisibility() == View.GONE

view.tag: view.getTag(). Use View.setTag() to set a Number or Boolean and call View.requestLayout() to trigger layout. Types other than Number and Boolean returns 0.

Expression

The syntax is the same as Java or C. Numbers can have units like 10dp, 15sp

(parent.height-view1.centerY)/2
100%-80dp
max(view1.right, view2.right)
screen.width<screen.height ? 64dp : 48dp
view1.visible && view2.visible ? max(view1.bottom, view2.bottom) : 0px

Operators (Order in precedence)

Functions

Changelog

1.2.0 (2016-4-6)

Show source code position in XML when throw Exceptions. (Syntax exception, Circular dependency, etc.)

1.1.0 (2016-3-20)

Initial release to jcenter. Including percentage, view reference, ?= expressions, logic operators.