Setting global styles for Views in Android

Let's say I want all the TextView instances in my app to have textColor="#ffffff". Is there a way to set that in one place instead of setting it for each TextView?

Actually, you can set a default style for TextViews (and most other built-in widgets) without needing to do a custom java class or setting the style individually.

If you take a look in themes.xml in the Android source, you will see a bunch of attributes for the default style for various widgets. The key is the textViewStyle (or editTextStyle, etc.) attribute which you override in your custom theme. You can override these in the following way:

Create a styles.xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="MyTheme" parent="android:Theme">
    <item name="android:textViewStyle">@style/MyTextViewStyle</item>
</style>

<style name="MyTextViewStyle" parent="android:Widget.TextView">
	<item name="android:textColor">#F00</item>
	<item name="android:textStyle">bold</item>
</style>
</resources>

Then just apply that theme to your application in AndroidManifest.xml:

<application […] android:theme="@style/MyTheme">…

And all your text views will default to the style defined in MyTextViewStyle (in this instance, bold and red)!

This was tested on devices from API level 4 onward and seems to work great.

There are two ways to do so:

1. Using styles

You can define your own styles by creating XML files on the res/values directory. So, let's suppose you want to have red and bold text, then you create a file with this content:

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <style name="MyRedTheme" parent="android:Theme.Light">
    <item name="android:textAppearance">@style/MyRedTextAppearance</item>
  </style>
  <style name="MyRedTextAppearance" parent="@android:style/TextAppearance">
    <item name="android:textColor">#F00</item>
    <item name="android:textStyle">bold</item>
  </style>
</resources>

You can name it like you want, for instance res/values/red.xml. Then, the only thing you have to do is using that view in the widgets that you want, for instance:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView
	style="@style/MyRedTheme"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="This is red, isn't it?"
    />
</LinearLayout>

For further reference, you can read this article: Understanding Android Themes and Styles

2. Using custom classes

This is another possible way to achieve this, and it would be to provide your own TextView that set the text color always to whatever you want; for instance:

import android.content.Context;
import android.graphics.Color;
import android.util.AttributeSet;
import android.widget.TextView;
public class RedTextView extends TextView{
	public RedTextView(Context context, AttributeSet attrs) {
		super(context, attrs);
		setTextColor(Color.RED);
	}
}

Then, you just have to treat it as a normal TextView in your XML file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<org.example.RedTextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="This is red, isn't it?"
    />
</LinearLayout>

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Whether you use one or another choice depends on your needs. If the only thing you want to do is modifying the appearance, then the best approach is the first. On the other hand, if you want to change the appearance and add some new functionality to your widgets, the second one is the way to go.

For default text color in TextView, set android:textColorTertiary in your theme to desired color:

<item name="android:textColorTertiary">@color/your_text_color</item>

Many other Android control's colors can be controlled using framework attributes, or support library attributes if you use support library.

For a list of attributes you can set, check out Android source code of styles.xml and themes.xml, or this very helpful gist by Dan Lew, try changing each value and see what they change on screen.

Define a style and use it on each widget, define a theme that overrides the android default for that widget, or define a string resource and reference it in each widget