Develop Reference

Why gravity doesn't center all of my views?

I was expecting all my TextView to be vertically centered in my RelativeLayout but this is only the case for the logo one. The others are anchored to the top of the latter.
Image
Here's my layout :
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="72dp"
android:gravity="center_vertical">
<TextView
android:id="#+id/logo"
android:layout_width="40dp"
android:layout_height="40dp"
android:text="TextView" />
<TextView
android:id="#+id/stop"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toEndOf="#+id/logo"
android:layout_toRightOf="#+id/logo"
android:text="TextView" />
<TextView
android:id="#+id/eta"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toEndOf="#+id/stop"
android:layout_toRightOf="#+id/stop"
android:text="TextView" />
<TextView
android:id="#+id/direction"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/stop"
android:layout_toEndOf="#+id/logo"
android:layout_toRightOf="#+id/logo"
android:text="TextView" />

The attribute layout_toEndOf performs layouting as follows:
Positions the start edge of this view to the end of the given anchor view ID. Link
Which means that all your TextViews start edges align with the logo's end.
As a starting point, just remove all layout_toEndOf attributes.
Then your layout should look something like this:
+--------------+
| | +-----------+
| | | stop |
| | +-----------+ +-----------+
| logo |/* no space */ | eta |
| | +-----------+ +-----------+
| | | direction |
| | +-----------+
+--------------+
More precisely, logo is vertically centered, same as eta. Since your layout code explictly places stop and direction directly to the right of logo, therefore direction is below stop.

Item views are not measured correctly when recycled in the RecyclerView

I have a scenario where, when views are recycled, the layout is incorrect. My row item layouts are as follows (note the wrap_content LinearLayout width, weight, and ellipsize):
<LinearLayout
android:id="#+id/header"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
>
<TextView
android:id="#+id/text1"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:ellipsize="middle"
android:singleLine="true"
tools:text="Ann really freaking long last name Droid"
/>
<TextView
android:id="#+id/text2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
<TextView
android:id="#+id/text3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
/>
</LinearLayout>
Desired behavior
row1 | 1-short-text | 2-text | 3-more-text
----------------------------------------------------
row2 | 1-short-text | 2-text | 3-more-text
----------------------------------------------------
row3 | 1-long-ellipsiz...text | 2-text | 3-more-text
----------------------------------------------------
row4 | 1-tiny | 2-text-longer | 3-more-text-blah
----------------------------------------------------
Actual behavior
row1 | 1-...et | 2-text | 3-more-text <-- ellipsized unnecessarily
----------------------------------------------------
row4 | 1-short-text | 2-text | 3-more-text
----------------------------------------------------
row2 | 1-long-ellipsiz...text | 2-text | 3-more-text
----------------------------------------------------
row3 | 1-tiny | 2-text-longer | 3-more-text-blah <-- spacing
----------------------------------------------------
What's the best way to go about solving this layout issue? Note: it works fine in a 4.1.1 emulator.

There's a known issue where TextViews don't re-measure in this scenario. I was able to solve this by doing the following when setting the data in my ViewHolder:
text1.setText("some-dynamic-text");
text1.requestLayout(); // <-- This is key... requestLayout after setting text.
When the view is recycled and new text was set, it wasn't laying out properly. Explicitly asking it to re-layout seems to re-calculate properly.

An alternative solution that seems to work is wrapping your troubling TextView in a FrameLayout.
...
<FrameLayout
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1">
<TextView
android:id="#+id/tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ellipsize="middle"
android:singleLine="true"/>
</FrameLayout>
...

Positioning Widgets in a Specific Arrangment

I'm quite new with Android programming in general, but I would like to know if there is a way to arrange my widgets in a particular way. Basically, I'm looking for the iOS equivalent of constraints, which will allow me to place to widgets centered horizontally and a specified distance from the bottom:
--------------------
| |
| |
| | <- android device
| |
| |
| | <- x is a button
| x x |
| |
--------------------

You can use a RelativeLayout with alignParentBottom="true"
Then you can add a padding in your relativelayout or a margin in your buttons a bit like this.
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:orientation:"horizontal"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerHorizontal="true"
android:layout_marginBottom="10dp">
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>
</RelativeLayout>

Positioning of textview for Android

Is there a way to position a textview to be slightly above a centerd android button? I don't want to hardcode values for a particular screen obviously, but something that will dynamically scale. The button will always be centered, however...
Thanks in advance!

Yes if your parent layout is a RelativeLayout you can position Views in relation to each other or to the parent here is a simple example (Warning didn't type this into IDE, may contain typo):
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<Button
android:id="#+id/mBtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="I am a Button!"
android:layout_centerInParent="true" />
<TextView
android:id="#+id/mTxt"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:text"Some Text"
android:layout_above="#+id/mBtn" />
</RelativeLayout>
That will make your layout look roughly like this:
________________________
| |
| |
| Some Text |
| [I am a Button!] |
| |
| |
|______________________|

how to put a view off-screen?

Is it able to put views to the left, but off-screen?
I want display three views(images) but only the second fit on the screen, something like:
+---------------------+
| Screen |
+-------+ +-------+ +-------+
| | | | | |
| image | | image | | image |
| | | | | |
+-------+ +-------+ +-------+
| |
+---------------------+
I would like to start be visible in this form.

You can use several approaches:
Gallery (http://developer.android.com/resources/tutorials/views/hello-gallery.html)
HorizontalScrollView (http://developer.android.com/reference/android/widget/HorizontalScrollView.html)
ViewPager (http://android-developers.blogspot.com/2011/08/horizontal-view-swiping-with-viewpager.html)
The choice now depends on what exactly you want to perform in your app.
Hope this helps!
In case you need something more specific, please shoot it!

In xml, try using:
android:paddingLeft

you can also do it with RelativeLayout. i think it is kind of like floating div in HTML, very funny.
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<RelativeLayout android:id="#+id/left_body"
android:gravity="center"
android:layout_alignParentLeft="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<ImageView android:background="#drawable/house"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</RelativeLayout>
<RelativeLayout android:id="#+id/right_body"
android:gravity="center"
android:layout_alignParentRight="true"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<ImageView android:background="#drawable/house"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</RelativeLayout>
<RelativeLayout android:id="#+id/main_body"
android:layout_toRightOf="#id/left_body"
android:layout_toLeftOf="#id/right_body"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<ImageView android:background="#drawable/house"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
</RelativeLayout>