Develop Reference

ConstraintLayout spacing between weighted Views?

I am trying to build an Android UI where I need 7 boxes with the days of the week. In order to do this, I decided to go with a ConstraintLayout in order to be able to auto resize my views on any screen.
I created a chain between all 7 views with the with the "spread_inside" attribute, with worked but since I had my views' widths set to wrap_content, due to the nature of TextViews the views did not have equal widths. So I tried making them have equal widths by setting all of 7 views' widths to 0dp. This works but leaves no space between the views. Is there a way to add some spacing between these 7 views? Or is there another way of achieving the "equal widths" to all 7 views while keeping the auto-resizing ability on any screen? Is this even possible with ConstraintLayout or should I keep using LinearLayout for this kind of things? (as seen in the last screenshot)
I want my views to shrink when the screen is small and to expand up to a level when the screen is big. Please see the screenshots below of how it looks now. I want to add an 8dp padding between each view (on a LinearLayout I achieve this by adding a transparent divider on the layout with 8dp width, as in the last screenshot)
How it should look, achieved using LinearLayout

if you want them to be all the same width you don't even need spread_inside, just set the width to 0dp and then add margins to the views. for example:
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
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="match_parent">
<View
android:id="#+id/view1"
android:layout_width="0dp"
android:layout_height="50dp"
android:layout_marginRight="4dp"
android:layout_marginLeft="8dp"
android:background="#ffff0000"
app:layout_constraintEnd_toStartOf="#+id/view2"
app:layout_constraintStart_toStartOf="parent"/>
<View
android:id="#+id/view2"
android:layout_width="0dp"
android:layout_height="50dp"
android:layout_marginRight="8dp"
android:layout_marginLeft="4dp"
android:background="#ff00ff00"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toEndOf="#+id/view1"/>
</android.support.constraint.ConstraintLayout>
keep in mind that space between views will be the sum of 2 margins, first and last view will have only 1 margin space, so you need to set them accordingly (like 4dp for margins between views and 8dp for first and last margin)

Android UI: "Smart" centering?

So I have a UI element (a single line of text) that I want horizontally centered with respect to the overall device -- unless/until it collides with other UI elements in the given view group / layout. At that point I'd like it to be either centered in the space remaining or pegged as close to being centered overall as possible without colliding. [When there's finally not enough space, then I want to use ellipses.]
Is there any way to achieve this using just standard Android layouts?
I'm currently achieving this via code that adjusts layout constraints when the view group's width changes, the text changes, or related UI elements become visible/invisible. It works fine, but I can't help thinking that some layout should just do this for me.

You can use a weighted horizontal LinearLayout like this:
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:gravity="center_horizontal"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:text="i am centered"
android:ellipsize="end"
/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="another widget"/>
.
.
.
</LinearLayout>
The TextView with width 0dp and weight 1 will use the remaining horizontal space.
You can add additional widgets to the LinearLayout, and the TextView will always take the remaining space.
For example, if you change the Visibility of the Button to GONE, you'll see the TextView will expand to use the whole width. Similarly, if you programmatically add new widgets to the LinearLayout, the available space for the TextView will adjust.
You can further add ellipsize options to control what happens when the text does not fit in the TextView size.

Inserting many views into one layout without them overflowing to the end of the screen

I'm looking for a way that I can dynamically add views into a layout (currently a LinearLayout) and that they won't overflow into the end of the screen and be hidden.
I can't use ScrollViews since it has to look like one sentence (It's a "fill the blanks" question).
I'm just looking for an idea on how to do this, not the code itself.
Thanks in advance, Shay.

If you are using linear layout than use linear layout with weights:
For example:
You have a LinearLayout with vertical orientation and you have 2 ImageViews inside it and you want these ImageViews always to take equal space.
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:weightSum="2"
android:orientation="vertical"
android:layout_gravity="center">
You can set the layout_weight of each ImageView to 1 and the weightSum in LinearLayout to 2 to achieve this.
<ImageView
android:layout_height="wrap_content"
android:layout_weight="1"
android:layout_height="0dp"/>
This will work correctly for any device without overflow into the end of the screen and be hidden

Have elements equally span entire width / height of their RelativeLayout

I have, say three buttons i would like to list below one another in a layout. Depending on the device, screen size, pixel density, orientation and so on, i would like the buttons to span the entire height of their parent layout. The buttons each have a fixed height (dp), so the spanning is more likely concerning the space between the buttons.
I saw several questions on various forums regarding how a LinearLayout is supposedly a fix for this problem, by nesting a layout for each element, having the layout span. I would very much like to avoid nesting layouts, and I'm using a RelativeLayout as of now, so if there is any way to go about it with this type of layout it will be of great help! :)
Additionally, I would like the top and bottom button to "touch" the parent layout border at the top and bottom, and the last (or rest) button to fill out the rest of the vertical space equally.
Thank you in advance.

I'm not entirely sure what you wish to achieve, but you should be able to do this using a LinearLayout & weights (so you don't have to nest multiple layouts).
If you want the 3 buttons to take up the entire parent of the screen just add a weight to each for example:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
android:id="#+id/button_one"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"/>
<Button
android:id="#+id/button_two"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"/>
<Button
android:id="#+id/button_three"
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"/>
</LinearLayout>

Try to set to topButton a field in XML:
android:layout_alignTop="true";
Try to set to middleButton a field in XML:
android:layout_centerVertical="true";
Try to set to bottomButton a field in XML:
android:layout_alignBottom="true";

How to create layout like this?

I have a horizontal LinearLayout, inside which I have 2 TextViews. Let's say that the LinearLayout's width is 320px. If the TextViews don't fit into the LinearLayout (they are together wider than 320px), I want to somehow achieve this:
The second TextView is fully displayed and is at the right edge of the LinearLayout
The first TextView is only shown partially, only first x characters are visible
What I mean:
[TextView1|TextView2_________________________] // this is normal
[VeryVeryL...|VeryVeryLongTextView2] // VeryVeryLongTextView1 is not fully visible

To get the effect you're requesting in the comments above, you could modify Mayra's solution to something like:
<LinearLayout ...>
<TextView android:layout_width="wrap_content"
android:maxWidth="20dp"
android:layout_height="wrap_content"/>
<TextView android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"/>
I think that will work. Weirdly, the maxWidth param is only present on a couple view classes, but TextView luckily is one of them. You'd think it'd be useful in more cases, so I'm not sure why it's not just available in the default view params.

Specify a specific width for your first textView (i.e, 20dp... note, it is better to use dp than hard coded pixels, to deal with multiple resolutions of devices), give your 2nd TextView a weight of 1. This tells it to take up the remaining space. For example:
<LinearLayout ...>
<TextView android:layout_width="20dp"
android:layout_height="wrap_content"/>
<TextView android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"/>
</LinearLayout>