SpringLayout - RelativeLayout on steroids.

The goal of this project is to create more reliable and feature-rich replacement for RelativeLayout. Apart from new features SpringLayout has better error reporting, so no more guessing what's wrong with your layout :-).

You can find the sample app on Google Play, just click on the logo below.

How to build

Simply update your gradle dependencies.

build.gradle:

dependencies {

  (...)
  compile('org.coderoller:springlayout:0.9.2') 
}
 

Improvements compared to RelativeLayout

New attributes

layout_alignCenterVertically:

Align center of the view vertically to the center of specified view.

layout_alignCenterHorizontally:

Align center of the view horizontally to the center of specified view.

layout_alignCenter:

Align center of the view both vertically and horizontally to the center of specified view.

Example:

<org.coderoller.springlayout.SpringLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:layout_width="match_parent"
  android:layout_height="50dp"
  android:background="@android:color/white">

<View

android:id="@+id/A"

android:layout_width="40dp"

android:layout_height="40dp"

android:background="#ffff0000"

android:layout_marginLeft="50dp"

app:layout_centerVertical="true"/>

<View

android:id="@+id/B"

android:layout_width="30dp"

android:layout_height="30dp"

android:background="#ff00ff00"

app:layout_alignCenter="@id/A"/>

<View

android:id="@+id/C"

android:layout_width="20dp"

android:layout_height="20dp"

android:background="#ff0000ff"

app:layout_alignCenter="@id/B"/>  </org.coderoller.springlayout.SpringLayout> 

layout_relativeWidth:

Specify the width of the view in percentage relative to parent width (excluding padding).

layout_relativeHeight:

Specify the height of the view in percentage relative to parent height (excluding padding).

Example:

<org.coderoller.springlayout.SpringLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:layout_width="match_parent"
  android:layout_height="50dp"
  android:background="@android:color/white">

<View

android:id="@+id/A"

android:layout_width="40dp"

android:layout_height="40dp"

android:background="#ffff0000"

app:layout_centerInParent="true"

app:layout_relativeWidth="75%"/>

<View

android:id="@+id/B"

android:layout_width="30dp"

android:layout_height="30dp"

android:background="#ff00ff00"

app:layout_alignCenter="@id/A"

app:layout_relativeWidth="50%"/>

<View

android:id="@+id/C"

android:layout_width="20dp"

android:layout_height="20dp"

android:background="#ff0000ff"

app:layout_alignCenter="@id/B"

app:layout_relativeWidth="25%"/>  </org.coderoller.springlayout.SpringLayout> 

Forward referencing

Forward referencing simply works as expected.

Try achieving the same in RelativeLayout (good luck with it :-)).

<org.coderoller.springlayout.SpringLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:app="http://schemas.android.com/apk/res-auto"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:background="@android:color/white" >

 <TextView

 android:id="@+id/X"

 android:layout_width="wrap_content"

 android:layout_height="20dp"

 android:background="#ffff0000"

 app:layout_alignParentLeft="true"

 android:text="X" />

 <TextView android:id="@+id/Y"

 android:layout_width="wrap_content"

 android:layout_height="20dp"

 app:layout_toRightOf="@id/X"

 app:layout_toLeftOf="@+id/Z"

 android:background="#ff00ff00"

 android:text="Y" />

<TextView

 android:id="@id/Z"

 android:layout_width="wrap_content"

 android:layout_height="20dp"

 app:layout_alignParentRight="true"

 android:background="#ff0000ff"

 android:text="Z" />
  </org.coderoller.springlayout.SpringLayout> 

Detailed error messages

SpringLayout will throw an exception when you do something wrong. For example it will inform you when you duplicate view constraints or introduce a circular dependancy.

Adapting width and height parameters

SpringLayout adapts view params a bit before rendering. For example if you specify the view height to be match_parent, then it implies that layout_alignParentTop and layout_alignParentBottom parameters are true. This works both ways, so if layout_alignParentTop and layout_alignParentBottom parameters are true then view height will be match_parent.

If the view has no vertical anchors defined, then it is set to alignParentTop. Same goes for horizontal anchors. If the view has no horizontal anchors defined, then it is set to alignParentLeft. Simply, there is no point of having a view without an anchor.

The wrap_content parameter normally tells the SpringLayout to take the child desired size as the final one. However if you define both constraints in one axis for a view which has wrap_content size in that axis, then SpringLayout will expand that view to meet the contraints.

Example:

<org.coderoller.springlayout.SpringLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:background="@android:color/white">

<View

android:id="@+id/A"

android:layout_width="40dp"

android:layout_height="40dp"

android:background="#ffff0000"

app:layout_alignParentLeft="true"/>

<View

android:id="@+id/B"

android:layout_width="40dp"

android:layout_height="40dp"

android:background="#ff00ff00"

app:layout_alignParentRight="true"/>

<View

android:id="@+id/C"

android:layout_width="wrap_content"

android:layout_height="match_parent"

android:background="#ff0000ff"

app:layout_toRightOf="@id/A"

app:layout_toLeftOf="@id/B"/>  </org.coderoller.springlayout.SpringLayout> 

Width and height weights (aka Springs)

SpringLayout introduces two new attributes layout_widthWeight and layout_heightWeight. Using them will introduce internal chain (horizontal or vertical) of views. The weight attribute tells SpringLayout how much of the empty space in the views chain the view should occupy. Weight attribute works only when corresponding layout size is WRAP_CONTENT. Apart from convenient way of specyfing view size, you can use the new attributes with empty views to organize other views in the layout. Such empty views will be called Springs from now on.

Springs introduced in SpringLayout slightly resemble Springs from GroupLayout that is available in Swing UI. They allow you to organize views on the screen in more advanced fashion without the need to nest layouts.

Let's say you want to center two Views horizontally on the screen. With RelativeLayout you would do something like this:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="match_parent"
  android:layout_height="60dp"
  android:background="@android:color/white">

<LinearLayout

android:layout_width="wrap_content"

android:layout_height="match_parent"

android:orientation="horizontal"

android:layout_centerHorizontal="true">

 <TextView

 android:id="@+id/A"

 android:layout_width="wrap_content"

 android:layout_height="match_parent"

 android:text="@string/sample_text"

 android:background="#ffff0000"/>

 <View

 android:id="@+id/B"

 android:layout_width="20dp"

 android:layout_height="match_parent"

 android:background="#ff00ff00"/>
  </LinearLayout>  </RelativeLayout> 

It works, but requires you to nest additional layout (that will only group those two views), which makes things slightly slower. In SpringLayout you can achieve the same by using Springs:

<org.coderoller.springlayout.SpringLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:layout_width="match_parent"
  android:layout_height="60dp"
  android:background="@android:color/white">

<View

android:id="@+id/spring_A"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

app:layout_widthWeight="1"/>

<TextView

android:id="@+id/A"

android:layout_width="wrap_content"

android:layout_height="match_parent"

android:background="#ffff0000"

android:text="@string/sample_text"

android:gravity="center"

app:layout_toRightOf="@id/spring_A"/>

<View

android:id="@+id/B"

android:layout_width="20dp"

android:layout_height="match_parent"

android:background="#ff00ff00"

app:layout_toRightOf="@id/A"/>

<View

android:id="@+id/spring_B"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

app:layout_toRightOf="@id/B"

app:layout_alignParentRight="true"

app:layout_widthWeight="1" />  </org.coderoller.springlayout.SpringLayout>  

Weight attributes work similar to layout_weight attribute that can be found in LinearLayout, however layout_widthWeight and layout_heightWeight apply only to empty space in the view chain. In the example above, the sum of weights in horizontal axis is 2, therefore spring_A and spring_B will both take 1/2 of empty space in the view chain left by views A and B.

Please note:

Using layout_widthWeight or layout_heightWeight will internally introduce a chain of Views. In the example above we will have a horizontal chain consisting of views (in order): spring_A, A, B, spring_B. Based on that the SpringLayout knows that empty space available for Springs will be chain width minus A width and B width.

Due to this fact, there are two things you have to keep in mind, when using these attributes:

• View chain head has to have start anchor (left for horizontal, top for vertical) and chain tail has to have end anchor (right for horizontal, bottom for vertical) defined. In other case chain size cannot be calculated and exception will be thrown. That's why spring_B has alignParentRight defined ( spring_A has no anchors defined therefore SpringLayout automatically defines alignParentTop and alignParentLeft for it).

• Views with weights are pointless (and won't work) when used inside a layout with wrap_content width or height (depends if the spring applies to vertical or horizontal chain), unless minWidth or minHeight parameter is specified. In other case empty space available to views with weights will be always 0.

• Currently the internal chains cannot divert, however this might change in future. This means that if you introduce a new view C that will be placed right of view B, then spring_B won't be attached to the chain since view B is succeeded by view C in the chain. So for the layout listed below the horizontal chain will consist of spring_A, A, B, C.

To illustrate, the snippet below will throw the following exception:

java.lang.IllegalStateException: Horizontal weight defined but never used, please review your layout. Remember that the chain of views cannot divert when using springs: Problematic view (please also check other dependant views): android.view.View{
a67c0e98 V.ED.... ......I. 0,0-0,0 #7f070009 app:id/C
}
, problematic layout: org.coderoller.springlayout.SpringLayout{
a67ae738 V.E..... ......ID 0,0-0,0
}
 

<org.coderoller.springlayout.SpringLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:layout_width="match_parent"
  android:layout_height="60dp"
  android:background="@android:color/white">

<View

android:id="@+id/spring_A"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

app:layout_widthWeight="1"/>

<TextView

android:id="@+id/A"

android:layout_width="wrap_content"

android:layout_height="match_parent"

android:background="#ffff0000"

android:text="@string/sample_text"

android:gravity="center"

app:layout_toRightOf="@id/spring_A"/>

<View

android:id="@+id/B"

android:layout_width="20dp"

android:layout_height="match_parent"

android:background="#ff00ff00"

app:layout_toRightOf="@id/A"/>

<View

android:id="@+id/spring_B"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

app:layout_toRightOf="@id/B"

app:layout_alignParentRight="true"

app:layout_widthWeight="1" />

 <View

android:id="@+id/C"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

app:layout_toRightOf="@id/B"

app:layout_alignParentRight="true"

app:layout_widthWeight="1" />  </org.coderoller.springlayout.SpringLayout>  

Attributes reference

Spring Layout

minHeight

Defines the minimum height of the layout.

minWidth

Defines the minimum width of the layout.

Spring Layout Children

layout_toLeftOf

Positions the right edge of this view to the left of the given anchor view ID.

layout_toRightOf

Positions the left edge of this view to the right of the given anchor view ID.

layout_above

Positions the bottom edge of this view above the given anchor view ID.

layout_below

Positions the top edge of this view below the given anchor view ID.

layout_alignLeft

Makes the left edge of this view match the left edge of the given anchor view ID.

layout_alignTop

Makes the top edge of this view match the top edge of the given anchor view ID.

layout_alignRight

Makes the right edge of this view match the right edge of the given anchor view ID.

layout_alignBottom

Makes the bottom edge of this view match the bottom edge of the given anchor view ID.

layout_alignCenter

Center will be aligned both horizontally and vertically with the given anchor view ID.

layout_alignCenterHorizontally

Center will be aligned horizontally with the given anchor view ID.

layout_alignCenterVertically

Center will be aligned vertically with the given anchor view ID.

layout_alignParentLeft

If true, makes the left edge of this view match the left edge of the parent.

layout_alignParentTop

If true, makes the top edge of this view match the top edge of the parent.

layout_alignParentRight

If true, makes the right edge of this view match the right edge of the parent.

layout_alignParentBottom

If true, makes the bottom edge of this view match the bottom edge of the parent.

layout_centerInParent

If true, centers this child horizontally and vertically within its parent.

layout_centerHorizontal

If true, centers this child horizontally within its parent.

layout_centerVertical

If true, centers this child vertically within its parent.

layout_relativeWidth

Width relative to parent (in percents).

layout_relativeHeight

Height relative to parent (in percents).

layout_widthWeight

Width weight of the spring. Used to calculate how much of the empty space in the chain the View should take. Works only when layout_width is WRAP_CONTENT.

layout_heightWeight

Height weight of the spring. Used to calculate how much of the empty space in the chain the View should take. Works only when layout_height is WRAP_CONTENT.