Develop Reference

Layout Attributes within Styles

I've been with a dilemma for a while that I don't know how to solve it properly. I want to use DRY (Don't Repeat Yourself), but not apply bad practices in styles (such as set the layout attributes inside them).
This is my case...
To have the text styles encapsulated in my projects, I usually use the following:
I have a style called Wrap_Content
<style name="WrapContent">
<item name="android:layout_width">wrap_content</item>
<item name="android:layout_height">wrap_content</item>
</style>
On the one hand, I have a style called Tv that inherits from WrapContent:
<style name="Tv" parent="WrapContent">
<item name="android:fontFamily">#font/font_foo</item>
<item name="android:textColor">#color/color_foo</item>
</style>
As you can see, apart, the Tv style has a default font and text color
If for example I want to use a font size of 15sp, I apply this style:
<style name="Tv.15">
<item name="android:textSize">15sp</item>
</style>
And so on...
Well, the issue is that all the TextView of my project I set wrap_content both width and height.
Therefore, doing things like this simplifies the layouts XML a lot and it increases the readability and grouping common behaviors.
Example:
<TextView
style="#style/Tv.15"
android:text="#string/foo"/>
And if in any case, I want to change any attribute, I have only to overwrite it from where I call it.
The dilemma is that I am mixing textAppearance styles with layout ones. I have thought about separating this ... but I have not just resolved the main issue, that I am setting layout attributes on it, something that I should know nothing more than its own view, and not its container.
But what does not convince me at all is to do something like this:
<style name="Tv">
<item name="android:fontFamily">#font/font_foo</item>
<item name="android:textColor">#color/color_foo</item>
</style>
<style name="Tv.15">
<item name="android:textSize">15sp</item>
</style>
<TextView
style="#style/Tv.15"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="#string/foo"/>
I don't want to repeat a million times with the same attributes if these are common. Or yes I see what it brings ... technical debt. Therefore, it does not seem like a valid option.
I have searched quite a lot and the truth is that I have not found anything that convinces me and I would like to reach something elegant, since it is something that I use at all times and I don't like it.
Well... what do you think about it?
Thank you so much!!!
EDITED 2019-11-08
I have thought a new approach adding a new layer of styles, the #style/TextAppearance. It is like this:
<style name="WrapContent">
<item name="android:layout_width">wrap_content</item>
<item name="android:layout_height">wrap_content</item>
</style>
<style name="TextAppearance">
<item name="android:fontFamily">#font/font_foo</item>
<item name="android:textColor">#color/color_foo</item>
</style>
<style name="TextAppearance.15">
<item name="android:textSize">15sp</item>
</style>
<style name="Tv" parent="WrapContent">
<item name="android:textAppearance">#style/TextAppearance</item>
</style>
<style name="Tv.15">
<item name="android:textAppearance">#style/TextAppearance.15</item>
</style>
This add a little bit of complexity to the system, but it splits the layout and the textAppearance attributes. Moreover, it allows use the TextAppearance style for buttons, editTexts an so on.

In our most recent Android Dev Summit, two of my colleagues gave a talk on how to use Theme & Style. We advice that you use Themes for View groups and their children and styles for simpler views. Perhaps your layout needs can be met by using Themes and then reserving styles for text appearances and such. Beyond that, efficacy should guide how you structure your style objects.

Set default font size in styles.xml

I am working on an android project.
I have a tabbed page and the title of the pages are very big.
What i want to do is to decrease font size by changing values in styles.xml
do you know if it is possible ?
The project is written with Xamarin, so i want to avoid to write some specific code, like renderers.
Thanks a lot

This is possible
styles.xml as follow:
<style name="FontTheme" parent="Theme.AppCompat.Light.NoActionBar">
<item name="android:textSize">20sp</item>
<item name="android:textColor">#color/black</item>
</style>
use code:
<TextView
style="#style/FontTheme"
android:layout_marginTop="100dp"
android:text="test1"/>

Android TimePickerDialog styling guide/docs?

I'm trying to style a TimePickerDialog for sdk 21+ (Lollipop). So far I've figured out how to change the default colorscheme in XML:
<style name="TimePickerTheme" parent="#style/Theme.AppCompat.Light.Dialog">
<item name="colorPrimary">#ff2d6073</item> <!-- no effect -->
<item name="colorPrimaryDark">#ff2d6073</item> <!-- no effect -->
<item name="colorAccent">#ff2d6073</item>
<item name="android:textColor">#ffD0D102</item>
<item name="android:textColorPrimary">#ffD0D102</item>
</style>
This works but I'm looking for a guide or documentation for all the properties I can change.
AccentColor does the basic color scheme
TextColorPrimary does the text color
But what property, for example, do I need to change the big text in the 'header' of the dialog (where the current selected time is displayed)?
Is there some documentation that lists all the possible things you can change?

After digging through the AOSP theme and style xml files and a lot of googling I made some progress. I am now able to style most(!) things.
So this is a partial answer, not all the way there yet. But here's how far I got:
You can see that I'm now able to theme the header, the un(!)selected time part (minutes in this case), the circle, the numbers in that circle and the 'hand' (or selector). Oh, and the buttons are styled, too.
Let me explain how I got things working, first: the important thing is that you can't override things directly from you app's theme OR from a (alert)dialog theme/style. You have to go from one to the next, so to speak.
Example:
AndroidManifest.xml: Set custom theme for app and/or activity
<activity>
android:theme="#style/Theme.MyTheme"
</activity>
values-v21/styles.xml: (where your custom theme resides): set the timePickerDialogTheme
<style name="Theme.MyTheme" parent="#style/Theme.AppCompat.Light">
<item name="android:timePickerDialogTheme">#style/TimePickerDialogTheme</item>
</style>
Then below that, define the timePickerDialogTheme and set the timePickerStyle:
<style name="TimePickerDialogTheme" parent="#style/Theme.AppCompat.Light.Dialog">
<item name="colorAccent">#ff2d6073</item> <!-- colorAccent here seems to work just fine? -->
<item name="android:timePickerStyle">#style/TimePickerDialogStyle</item>
</style>
Now you can define most of the styling here..
<style name="TimePickerDialogStyle" parent="#android:style/Widget.Material.Light.TimePicker">
<item name="colorAccent">#ff2d6073</item> <!-- colorAccent here seems to work just fine? -->
<item name="android:timePickerMode">clock</item>
<item name="android:headerBackground">#ff2d6073</item>
<item name="android:headerTimeTextAppearance">#style/TextAppearance.TimePickerDialogStyle.TimeLabel</item> <!-- TimePicker Time *TextAppearance* -->
<item name="android:numbersTextColor">#ff000000</item>
<item name="android:numbersSelectorColor">#ff2d6073</item>
<item name="android:numbersBackgroundColor">#ffdddddd</item>
</style>
The important line in the above is:
<item name="android:headerTimeTextAppearance">#style/TextAppearance.TimePickerDialogStyle.TimeLabel</item>
Because if you want to style the text (well, time, actually) in the header you need to define the headerTimeTextAppearance:
<style name="TextAppearance.TimePickerDialogStyle.TimeLabel" parent="#android:style/TextAppearance.Material">
<item name="android:textSize">60sp</item> <!-- from -->
<item name="android:textColor">#ffD0D102</item>
</style>
Now, if you take a look at the Widget.Material.TimePicker in AOSP styles.xml (ctrl-f 'timepicker' until you find it) you'll notice a bunch of other properties that you should be able to modify:
headerTimeTextAppearance
headerAmPmTextAppearance
headerSelectedTextColor
headerBackground
numbersTextColor
numbersBackgroundColor
amPmTextColor
amPmBackgroundColor
amPmSelectedBackgroundColor
numbersSelectorColor
Most of these work (as long as you prepend 'android:' for each of them) BUT I could not get 'headerSelectedTextColor' to work. I got a compile error saying something like "could not match property bla bla". Also, if you look at my example above, I hardcoded the textSize for the 'headerTimeTextAppearance' property because the '#dimen/timepicker_ampm_label_size' value threw errors.
In short: most of the things are listed above and how to get them working. But not all is clear. So I'd still see that complete documentation/guide :)

Android TimePicker material style with custom colors below, you can see http://www.zoftino.com/android-timepicker-example for TimePicker usage and styles.
<style name="MyAppThemeFour" parent="Theme.AppCompat.Light">
<item name="android:timePickerDialogTheme">#style/MyTimePickerDialogStyle</item>
</style>
<style name="MyTimePickerDialogStyle" parent="#style/ThemeOverlay.AppCompat.Dialog.Alert">
<item name="showTitle">false</item>
<item name="colorControlActivated">#ffd600</item>
<item name="colorAccent">#b71c1c</item>
<item name="android:textColorPrimary">#43a047</item>
<item name="android:textColorSecondary">#f44336</item>
</style>

When using version 1.5.0 of the Material Design Library for Android, I've found that I can get most of the theming with using this particular style:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="MyTimePickerTheme" parent="ThemeOverlay.MaterialComponents.TimePicker">
<item name="android:textColor">#FF121212</item>
<item name="android:textColorPrimary">#FF121212</item>
<item name="android:textColorSecondary">#FFF9F9F9</item>
<item name="colorAccent">#FF121212</item>
<item name="colorControlNormal">#FF121212</item>
<item name="colorPrimary">#FF121212</item>
<item name="colorSurface">#FFF9F9F9</item>
</style>
</resources>
This will yield in a generic - non colored - Dialog which works for white theme. For dark theme, simply invert the colors.
I've also asked here to have dynamic theming supported for this component.
Example screenshot using the above style:

Change the line color used in listSeparatorTextViewStyle

I have the following code
<TextView
android:text="#string/hello"
style="?android:attr/listSeparatorTextViewStyle" />
and I will get the following effect.
However, I am not happy with the color line. I would like to have something like
I would like it to have blue color line as in holo. I try the following custom style.
<style name="MyOwnListSeperatorTextViewStyle">
<item name="android:background">#android:drawable/list_section_divider_holo_light</item>
<item name="android:textAllCaps">true</item>
<!-- Copy from Widget.TextView.ListSeparator -->
<item name="android:background">#android:drawable/dark_header_dither</item>
<item name="android:layout_width">match_parent</item>
<item name="android:layout_height">wrap_content</item>
<item name="android:textStyle">bold</item>
<item name="android:textColor">?textColorSecondary</item>
<item name="android:textSize">14sp</item>
<item name="android:gravity">center_vertical</item>
<item name="android:paddingLeft">8dip</item>
</style>
But it won't work, as I get the following error.
error: Error: Resource is not public. (at 'android:background' with value '#android:drawable/dark_header_dither').
Have idea how can I change the line color used in listSeparatorTextViewStyle?

I needed to do this to override the typical Holo Spinner style (I didn't want the underlined item - i just wanted the arrow), and I think this can be overridden in precisely the same manner:
First off, you want to find the item you wish to override in the android styles source. There is an incredibly useful SO answer that contains all of the styles (and the names to override them) right here: Set Dialog theme to parent Theme in Android
I believe yours is the following line:
<item name="listSeparatorTextViewStyle">#android:style/Widget.Holo.Light.TextView.ListSeparator</item>
This takes us on a journey to find the style Widget.Holo.Light.TextView.ListSeparator which should live somewhere on your very own computer! But I'll make it easy and just c&p it:
<style name="Widget.Holo.Light.TextView.ListSeparator" parent="Widget.TextView.ListSeparator">
<item name="android:background">#android:drawable/list_section_divider_holo_light</item>
</style>
Now, you probably want to leave well enough alone, and just look at that background drawable. You will find it is a grey 9patch file that looks like the sinister grey line you seek to avoid.
We need to override this. I am sure there are a number of ways to do this, but I do so by customizing the theme of the application. Here is the themes.xml file:
<style name="AppTheme" parent="#android:style/Theme.Holo.Light.NoActionBar">
<item name="android:listSeparatorTextViewStyle">#style/MyOwnListSeperatorTextViewStyle</item>
</style>
<style name="MyOwnListSeperatorTextViewStyle" parent="Widget.TextView.ListSeparator">
<item name="android:background">#drawable/make_your_own_blue_9_patch_here</item>
</style>
Notice how we used the listSeparatorTextViewStyle from that previous SO post? And the parent of the custom style is the Widget.TextView.ListSeparator from android's style source? All very important.
Now you just need to apply this theme to your app, but I am assuming you have a theme already. If you haven't already, you will need to make your own 9patch but I would just look at the list_section_divider_holo_light.9.png file on your computer, and make the grey parts blue, and then make a copy and place it into your own drawables folder.
Hope this works and is helpful!

What do i have to do to make a style for an activity that just affects the textviews?

Actually i have two questions.
Question 1.
I have made a style for a TextView
http://pastebin.com/q9hj26JX (Couldn't paste xml code here, it just went invisible)
To add this style i do:
http://pastebin.com/QdGmjQ0z
But instead of doint this, there must be a way to add this style to all the TextView in an activity? I have seen something like "Widget.TextView", but i have not found any good tutorial or documentation on it yet.
So can someone please give me an example, if it is possible.
Now for question number 2:
I don't get any intellisense while creating styles. Does it not exist for style creation?
Thanks in advance!

Please red about THEMES in android http://developer.android.com/guide/topics/ui/themes.html
The THEME is a style for whole activity and sets in Android Manifest.
Hope, it help you!
UPDATE:
Try this code:
<?xml version="1.0" encoding="utf-8"?>
<resources xmlns:android="http://schemas.android.com/apk/res/android">
<style name="small_describing_text" parent="#android:style/TextAppearance.Medium">
<item name="android:layout_width">fill_parent</item>
<item name="android:layout_height">wrap_content</item>
<item name="android:gravity">center_horizontal</item>
<item name="android:layout_marginTop">0dp</item>
<item name="android:textSize">10dp</item>
<item name="android:textColor">#FF0000</item>
</style>
<style name="MyTheme" parent="android:Theme.Light">
<item name="android:textViewStyle">#style/small_describing_text</item>
</style>
</resources>
Don't forget add this theme in Manifest for your activity!!!

You might want to have a look at my blogpost where I've explained theming and styling: http://aproblemlikemaria.wordpress.com/2011/09/26/theming-and-styling-in-android/