Develop Reference

Is constraint layout more flexible in locating views in Android Studio?

Both constraint and relative view groups support relative positioning of a view wrt other.
Relative layout provides 4 different attributes : layout_toRightOf / toLeftOf / toTopOf / toBottomOf ,
and Constraint provides many combinations of format " layout_constraintTop_toTopOf "
BUT can’t we place the views at any position just using the 4 attributes of Relative layout ?
In what way is Constraint layout more responsive ?

According to Google Developers ConstraintLayout has better performance than RelativeLayout. In addition (as you've mentioned) it's more advanced than RelativeLayout and allows you to build your Layout more precisely with all these additional constraints options. What's more, if you set the view A's width or height to match_constraint (0dp), and set its end constraint to start of view B, the A's width or height can be dynamically scaled when B's visibility is gone.
Any view inside ConstraintLayout requires only two constraints for X and Y axis e.g. layout_constraintTop_toTopOf and layout_constraintStart_toStartOf.

Android: how to align element 2 to the right of element 1 while only allowing element 2 to take up as much space as needed

I am trying to align two layouts horizontally but can't seem to get it working. The conditions I need are:
Layout 1 needs to fill up the whole width EXCEPT for the width that layout 2 requires
Layout 2 needs to have a width of 21dp and right / left margin of 17dp.
I can't take a picture because of my job, but here' some ascii art to illustrate what I want:
I attempted using a dummy View between the two layouts so that I could use a relative layout, but that wasn't quite working for me..so any suggestions?
Thanks!

<RelativeLayout layout_width="match_parent">
<Layout1 layout_width="match_parent" layout_toLeftOf="#+id/layout2"/>
<Layout2 id="#id/layout2" layout_width=21dp layout_alignParentRight="true" layout_marginLeft="17dp" layout_marginRight=17dp/>
</RelativeLayout>
Add in the rest of the parameters as needed

Try using a horizontal LinearLayout and set android:layout_weight="1" for layout 2. Like this layout 2 should keep it's size and layout 1 will fill the rest of the available space.

Equal width and height layout constraint

I have the following requirement in Android:
Given a horizontal LinearLayout, I have five buttons in it. All the buttons should have equal width and height. The height of each button is same as their parent LinearLayout and spacing between them should remain constant. The height of LinearLayout is not constant and depends on form factor and other layouts sizing. Therefore, I can not assign fixed with/height to each button.
While I can easily achieve that very easily in iOS with the help of constraints, I am not sure how to achieve this in Android at design time. Is there some way to achieve this or is it possible programatically only?

The height of each button is same as their parent LinearLayout
Set the height to match_parent
For your width, you'll have to calculate the screen size programmatically and set the widths accordingly. See this question.

Try this . As you have a horizontal LinearLayout with 5 buttons, for equal spacing of all buttons, you must first allocate the space to each button of of the total space available like this..
<LinearLayout
android:weightSum="5"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<Button
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="allocate it programatically"
/>
This button shown above has to be for all 5 buttons u have. The idea allocating weight sum of 5 to LinearLayout and then dividing it as 1 to each button. Note the width here for the button should be 0dp.
Then dynamically change your button Height and Width per your requirement

Unfortunately no typical layout in Android seems to have the concept of this kind of layout constraint (square like elements).
It's the layout that ultimately determines the sizes of their children. Therefore if you want that you have to write your own layout implementing this constraint.
For this extend ViewGroup and in onLayout enforce that width of the children or a specific children equals height. You could even invent your own LayoutParams for this task. See the documentation of ViewGroupfor a general example. The exact implementation very much depends on which other requirements you have for your layout.

In framelayout, if I want to put a view in the position that starts from 1/2 of the screen width

In framelayout, if I want to put a view in the position that starts from 1/2 of the screen width. How can I do it? Thanks.

You can accomplish that in multiple ways. It only depends if you really need to stick with the FrameLayout.
Two easiest would be those:
FrameLayout - you would need to know whats the width of the layout (so if your layout is wrap_content it might get tricky). Set your view's gravity to left, and set its margin_left to half of the layout's width.
LinearLayout - either put it inside your FrameLayout (not very good practice), or (if you can) swap it with your FrameLayout. Set it's orientation to horizontal, add dummy view with width = 0dp, weight = 1. Then add your view with the same values for width and weight.

android app - make view only take up portion of parent view

I have a background image on my app, and I want my listview to be in the form of a window that overlays the background image. Sort of like the the form which has a white filter in this picture:
http://25.media.tumblr.com/ad75c4a9dad9650ed53d754712f4fbb2/tumblr_mgemxiU2W01r2wjwko2_1280.png
I currently have a listview defined in xml with:
android:layout_width="fill_parent"
android:layout_height="fill_parent"
and a semi transparent color as its background. This is great, but it takes up the whole screen, since it fills the parent width and height. What is the best way to make it slightly smaller than the parent's dimensions so that it is say, (fill_parent - some relative value) height and width?

Use margin in a layout to make it smaller relative to the parent layout and other child's

Use a FrameLayout as a parent, then add your ListView and set width and height to wrap_content. Now it should "float" above the other views inside the FrameLayout. You can use padding and margin to set its position.