Develop Reference

Background Recyclerview shows incorrectly after changing to Light/ Dark theme from Android App

Anyone can help me?
I'm developing the Light and Dark theme function in the android app, everything goes fine, but the background of Recyclerview shows incorrectly.
The root background of xml file is White color and I didn't set background for recyclerview in xml. However, after changing from Light to Dark or Dark to Right=> background of recyclerview automatically change to a strange color(this color didn't see in my color.xml resource). I tried to set background of Recyclerview to #null or transparent in code and xml file as well but the background of recyclerview didn't remove that strange color.
So anyone knows exactly the reason why, please help me and much appreciated. Thanks
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I am guessing you are using the DayNight Theme. If so you should have to themes.xml folder in res, one is called as mentioned and the other is with the extension (night). There you can define a color in both xml files. It has the same name but different color values like this:
<style name="AppTheme" parent="Theme.AppCompat.DayNight">
<item name="colorPrimaryDark">#ffffff</item> <!-- you normally shouldn't hardcode color -->
</style>
The same for your folder (night):
<style name="AppTheme" parent="Theme.AppCompat.DayNight">
<item name="colorPrimaryDark">#000000</item> <!-- you normally shouldn't hardcode color -->
</style>
The idea is to have one attribute name that contains 2 colors and takes the correct one if needed. For futher understanding I suggest to take a look at this reference to get more familiar with Themes and Styles. Now you set up your Day and Night files properly, you can implement it by using it in your recyclerView as follows:
android:background="?attr/colorPrimaryDark"
Another tip is to make custom colors in multiple colors.xml files to make them for more unique use. In this case colorPrimaryDark effect your whole app. It is also suggested to modify layouts and the visuals of widgets to take effect only on those. (e.x. your recyclerView). In my app I used colorPrimaryDark for all Background (that should be same for more clean design). I think you get the keypoint. Take a look around the net and this forum and you will find your final design strategy. Cheers! :)

Managing multiple button selectors?

My calculator app consists of 30 buttons. I want to provide themes for the calculator keypad. A theme changes button background (gradients, not image backgrounds) and font. Some themes have the same color for all buttons while some have a color for numbers, another color for operators and so on.
The color change is using selectors from res/drawable/*.xml
How do I change the theme via the code?
Hopefully avoiding typing:
button.setBackground(Drawable background);
button.setTypeface(font);
30 times. And if I have 5 themes, then 30 * 5 * 2 = 300 lines of codes!!
I'm new to this and if there is no other way I'll go with the 150 lines.
Also how do I save the user theme selection? Using preferences?

You can create a custom XML theme which will change all of your XML components. After creating a new theme, go into the Android Manifest file and change the theme. For example:
<activity
android:name="com.myapp.MyActivity"
...
android:theme="#style/MyCustomTheme" />
To create the theme, go to res/values/themes.xml and create a new theme with an identifier:
<resources>
...
<style name="MyCustomTheme" parent="android:style/Theme">
<item name="android:textColorPrimary">#ffff0000</item>
</style>
...
</resources>
By using this method, you can create an extensive library of different themes and change to what theme you want.
NOTE: This is not just for changing the background, but it can also be used to change the theme of the buttons. Visit this website for more information:
http://janrain.com/blog/introduction-to-android-theme-customization/
EDIT: As that user commented, it is possible that you can put the function to change the theme of the button in a for() loop.
For your case, I have derived this from the link above. It will change the texture of the buttons in your XML file rather than in Java.
"Using a Custom Nine-Patch With Buttons
A nine-patch drawable is a special kind of image which can be scaled in width and height while maintaining its visual integrity. Nine-patches are the most common way to specify the appearance of Android buttons, though any drawable type can be used.
Example nine-patch PNG.
Notice the one pixel black lines around the edge, they control the scaling of the image.
Save this bitmap as MyApplication/res/drawable/my_nine_patch.9.png
Define a new style (you can define the new style in the same file that you defined your custom theme from Creating a Custom Android Theme above) …:
<resources>
...
<style name="MyCustomButton" parent="android:Widget.Button">
<item name="android:background">#drawable/my_nine_patch</item>
</style>
...
</resources>
Apply the new button style to the buttonStyle attribute of your custom theme:
<resources>
...
<style name="MyCustomTheme" parent=...>
...
<item name="android:buttonStyle">#style/MyCustomButton</item>
</style>
...
</resources>
Now the buttons in the activities your theme is applied to have custom images. However, you may notice that they don’t change appearance when selected. Read Selector Drawables below for an introduction to using multiple drawables to define one drawable that changes based on state."
From here, you can change certain components of the theme (such as the button texture as an image).
After you have a theme that looks good, apply it in the Android Manifest as I mentioned above.
I will FURTHER edit this if it still does not answer your question.

Define my customized theme for dialogs

I finally understood what themes are and how to apply them to a dialog.
I would like to create a theme and I need help from you to achieve what I want. I basically want to create a theme to apply to alert dialogs and to dialogs throughout my application.
In my theme, I need to define the title background color, title text size, main body background color and main body text size. What items should I use?
Here is the starting code to prove that I put some work into it :)
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="myGeneralDialogStyle" parent="#android:style/Theme.Dialog">
<item name="?"></item>
</style>
</resources>

IF all you got is the XML you shown above, then if your questions is about this "?" sign in name="?" part, then only thing you can use here are defined attributes. In your case you can i.e. use android:* ones. If you need to define own attributes then see here: Declaring a custom android UI element using XML

Android style descriptions

I tried changing the appearance of a spinner and I partly succeeded. I'm doing this via overriding parts of the theme. I managed to change the text size of the spinner item (i.e. the text size in the drop down button) with my themes.xml and styles.xml:
My themes.xml file looks like this:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="CustomTheme" parent="#android:Theme.Holo.Light">
<item name="android:windowActionBar">false</item>
<item name="android:windowNoTitle">true</item>
<item name="android:spinnerItemStyle">#style/CustomSpinnerItem</item>
</style>
</resources>
My styles.xml file looks like this:
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="CustomSpinnerItem" parent="#android:Widget.TextView.SpinnerItem">
<item name="android:textAppearance">#style/CustomTextAppearance</item>
</style>
<style name="CustomTextAppearance">
<item name="android:textSize">30dp</item>
</style>
</resources>
However I cannot find the attributes that are responsible for the text appearance of the items in the dropdown list of the spinner. I tried dropDownItemStyle amongst other things. In my opinion the attribute names are not self-explanatory, so I wanted to know whether there is a documentation of what attribute does what in a style to find out which attributes to override. I found it very cumbersome to trace back all the styles used in a theme via the themes.xml and styles.xml of the platfrom and then try to find the right attributes via trial and error.
I know that one can change the appearance by passing layouts to the adapter, however, this is not really what I was looking for, since (as far as I know), you can only use inheritance in styles and not in layout xml files. If I created a custom layout for the adapter I'd have to create 9-patch images etc., which I think is a bit too time consuming in case I only want to change the text size.
Of course it's possible that I misunderstood the whole concept, since I'm new to Android ;)

You probably have found out the answer since you asked but for others looking at similar questions:
I do not know of a list of attribute names with good explanation of what they do (R.attr's page mostly gives information that is already in the name) but the way I do it is:
Start from the element I give to setDropDownViewResource(), in my case: android.R.layout.simple_spinner_dropdown_item and find.
Find its layout definition in \sdk\platforms\android-17 (specific platform version to avoid redundant results).
Get its style from the layout file. In this case: ?android:attr/spinnerDropDownItemStyle
We now have the attribute name we need.
It's better to do it that way rather than try to guess what attribute to use because you know which attribute the system itself use so it's very likely to be the correct one (unless there's a bug).
If I created a custom layout for the adapter I'd have to create
9-patch images etc.
Well, no, the layout determines what kind of GUI element you would have (a textfield, a spinner, an imagebutton, a custom element...), not how they are styled (nine-patch backgrounds, text colors...), so you still would have to mess with styles to get the right appearance.
For example, for visual consistency I ported the button, checkbox and spinner style from Theme.Holo to Gingerbread, yet I did not mess with layout, all I did was the aforementioned steps plus looking up the result (spinnerDropDownItemStyle in the above example) in themes.xml, which gave me the style name (e.g.: Widget.Holo.DropDownItem.Spinner).
Then I looked that up in styles.xml and imported it (and any parent*) in my project's styles.xml, searching and copying any Holo specific reference in my project and adjusting the namespace accordingly (add android: to attributes and replace ?android:attr with #style for what I copy to my styles.xml file).
So far I haven't had to mess with layouts at all (even the presence of radio buttons in spinner dialogs on Gingerbread is determined by an xml attribute: android:checkMark).
If a style has no parent attribute (like Widget.Holo.DropDownItem.Spinner) then its parent is the same style minus the last element (e.g.: Widget.Holo.DropDownItem)

Android Styling/Theming of just Search Dialog

tl;dr: White text style in app theme being picked up by search dialog, making search text invisible.
I'm struggling mightily with what seems like a trivial issue.
My app is using a dark background, and I've tweaked the text color to be brighter than the standard gray using #EEEEEE.
I've implemented a Search Dialog (pre-Honeycomb) and it works well, but the text in the search dialog picks up the same #EEEEEE so it is essentially invisible. Even the context menu displayed when I long press the search text picks up #EEEEEE, so the text there is invisible as well.
I'm tearing my hair out, and I'm running out of hair.
Style:
<style name="master" paret="#android:style/Theme.NoTitleBar">
<item name="android:textColor">#EEEEEE</item>
<item name="android:windowNoTitle">true</item>
</style>
Manifest:
<application android:icon="#drawable/icon"
android:label="#string/app_label"
android:theme="#style/master"
android:hardwareAccelerated="true"
android:debuggable="true">

The attribute android:textColor is not meant to be used inside theme styles, it is primarily useful in widget and text appearance styles.
If you want to change the general text colors through a theme, use instead the android:textColor* family of attributes. There are quite a few of them, and different Views use them differently, so it takes a bit of experimentation (or careful studying of the Android source code) to to get it all right. The android.R.attr documentation lists them all. Look for the attributes that begin with textColor....
To get you started, try this theme, it will behave better by not affecting the Search Dialog colors at all, which seems to be what you want. By the way, you don't need to set android:windowNoTitle to true in your theme as your parent theme does that already:
<style name="master" parent="#android:style/Theme.NoTitleBar">
<item name="android:textColorPrimary">#EEEEEE</item>
<item name="android:textColorSecondary">#EEEEEE</item>
<item name="android:textColorTertiary">#EEEEEE</item>
</style>

I got into the same problem as you. I've looked around for a solution but it seems that you just can't change the textColor of a dialog. My solution was creating a custom dialog based on this tutorial: http://blog.androgames.net/10/custom-android-dialog/
I extended this a lot based on the Android source code, always using the same method names etc to make it a bit easier.
It is not ideal, but as far as I know it's the best option...
EDIT: for your problem there might be a simpler solution: don't put the textColor into the theme, but put it in a style. I don't know how you're styling your app but I'm usually creating a "master-style" which all the others inherit from (direct or indirect). You could then put the textColor in there so all your standard dialogs will still have the standard textColor.