How to retrieve style attributes programmatically from styles.xml

Question

Currently I'm using either a WebView or a TextView to show some dynamic data coming from a webservice in one of my apps. If the data contains pure text, it uses the TextView and applies a style from styles.xml. If the data contains HTML (mostly text and images) it uses the WebView.

However, this WebView is unstyled. Therefor it looks a lot different from the usual TextView. I've read that it's possible to style the text in a WebView simply by inserting some HTML directly into the data. This sounds easy enough, but I would like to use the data from my Styles.xml as the values required in this HTML so I won't need to change the colors et cetera on two locations if I change my styles.

So, how would I be able to do this? I've done some extensive searching but I have found no way of actually retrieving the different style attributes from your styles.xml. Am I missing something here or is it really not possible to retrieve these values?

The style I'm trying to get the data from is the following:

<style name="font4">
    <item name="android:layout_width">fill_parent</item>
    <item name="android:layout_height">wrap_content</item>
    <item name="android:textSize">14sp</item>
    <item name="android:textColor">#E3691B</item>
    <item name="android:paddingLeft">5dp</item>
    <item name="android:paddingRight">10dp</item>
    <item name="android:layout_marginTop">10dp</item>
    <item name="android:textStyle">bold</item>
</style>

I'm mainly interested in the textSize and textColor.

Answer 1

It is possible to retrieve custom styles from styles.xml programmatically.

Define some arbitrary style in styles.xml:

<style name="MyCustomStyle">
    <item name="android:textColor">#efefef</item>
    <item name="android:background">#ffffff</item>
    <item name="android:text">This is my text</item>
</style>

Now, retrieve the styles like this

// The attributes you want retrieved
int[] attrs = {android.R.attr.textColor, android.R.attr.background, android.R.attr.text};

// Parse MyCustomStyle, using Context.obtainStyledAttributes()
TypedArray ta = obtainStyledAttributes(R.style.MyCustomStyle, attrs);

// Fetch the text from your style like this.     
String text = ta.getString(2);

// Fetching the colors defined in your style
int textColor = ta.getColor(0, Color.BLACK);
int backgroundColor = ta.getColor(1, Color.BLACK);

// Do some logging to see if we have retrieved correct values
Log.i("Retrieved text:", text);
Log.i("Retrieved textColor as hex:", Integer.toHexString(textColor));
Log.i("Retrieved background as hex:", Integer.toHexString(backgroundColor));

// OH, and don't forget to recycle the TypedArray
ta.recycle()

Answer 2

The answer @Ole has given seems to break when using certain attributes, such as shadowColor, shadowDx, shadowDy, shadowRadius (these are only a few I found, there might be more)

I have no idea as to why this issue occurs, which I am asking about here, but @AntoineMarques coding style seems to solve the issue.

To make this work with any attribute it would be something like this

---

First, define a stylable to contain the resource ids like so

attrs.xml

<resources>     
    <declare-styleable name="MyStyle" >
        <attr name="android:textColor" />
        <attr name="android:background" />
        <attr name="android:text" />
    </declare-styleable>
</resources>

Then in code you would do this to get the text.

TypedArray ta = obtainStyledAttributes(R.style.MyCustomStyle, R.styleable.MyStyle);  
String text = ta.getString(R.styleable.MyStyle_android_text);

The advantage of using this method is, you are retrieving the value by name and not an index.

Answer 3

I was not able to get the earlier solutions to work.

My style is:

<style name="Widget.TextView.NumPadKey.Klondike" parent="Widget.TextView.NumPadKey">
    <item name="android:textSize">12sp</item>
    <item name="android:fontFamily">sans-serif</item>
    <item name="android:textColor">?attr/wallpaperTextColorSecondary</item>
    <item name="android:paddingBottom">0dp</item>
</style>

The obtainStyledAttributes() for android.R.attr.textSize gives String results of "12sp" which I then have to parse. For android.R.attr.textColor it gave a resource file XML name. This was much too cumbersome.

Instead, I found an easy way using ContextThemeWrapper.

TextView sample = new TextView(new ContextThemeWrapper(getContext(), R.style.Widget_TextView_NumPadKey_Klondike), null, 0);

This gave me a fully-styled TextView to query for anything I want. For example:

float textSize = sample.getTextSize();

Answer 4

The answers from Ole and PrivatMamtora didn't work well for me, but this did.

Let's say I wanted to read this style programmatically:

<style name="Footnote">
    <item name="android:fontFamily">@font/some_font</item>
    <item name="android:textSize">14sp</item>
    <item name="android:textColor">@color/black</item>
</style>

I could do it like this:

fun getTextColorSizeAndFontFromStyle(
    context: Context, 
    textAppearanceResource: Int // Can be any style in styles.xml like R.style.Footnote
) {
    val typedArray = context.obtainStyledAttributes(
        textAppearanceResource,
        R.styleable.TextAppearance // These are added to your project automatically.
    )
    val textColor = typedArray.getColorStateList(
        R.styleable.TextAppearance_android_textColor
    )
    val textSize = typedArray.getDimensionPixelSize(
        R.styleable.TextAppearance_android_textSize
    )

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        val typeface = typedArray.getFont(R.styleable.TextAppearance_android_fontFamily)

        // Do something with the typeface...

    } else {
        val fontFamily = typedArray.getString(R.styleable.TextAppearance_fontFamily)
            ?: when (typedArray.getInt(R.styleable.TextAppearance_android_typeface, 0)) {
                1 -> "sans"
                2 -> "serif"
                3 -> "monospace"
                else -> null
            }

        // Do something with the fontFamily...
    }
    typedArray.recycle()
}

I took some inspiration from Android's TextAppearanceSpan class, you can find it here: https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/text/style/TextAppearanceSpan.java

Answer 5

With Kotlin, if you include the androidx.core:core-ktx library in your app/library...

implementation("androidx.core:core-ktx:1.6.0") // Note the -ktx

...you can have either of the following (no need for you to recycle the TypedArray):

// Your desired attribute IDs
val attributes = intArrayOf(R.attr.myAttr1, R.attr.myAttr2, android.R.attr.text)

context.withStyledAttributes(R.style.MyStyle, attributes) {
    val intExample = getInt(R.styleable.MyIntAttrName, 0)
    val floatExample = getFloat(R.styleable.MyFloatAttrName, 0f)
    val enumExample = R.styleable.MyEnumAttrName, MyEnum.ENUM_1 // See Note 1 below
    // Similarly, getColor(), getBoolean(), etc.
}

context.withStyledAttributes(R.style.MyStyle, R.styleable.MyStyleable) {
    // Like above
}

// attributeSet is provided to you like in the constructor of a custom view
context.withStyledAttributes(attributeSet, R.styleable.MyStyleable) {
    // Like above
}

Note 1 (thanks to this answer)

For getting an enum value you can define this extension function:

internal inline fun <reified T : Enum<T>> TypedArray.getEnum(index: Int, default: T) =
    getInt(index, -1).let { if (it >= 0) enumValues<T>()[it] else default }

Note 2

The difference between -ktx dependencies like androidx.core:core and androidx.core:core-ktx is that the -ktx variant includes useful extension functions for Kotlin. Otherwise, they are the same.

_{Also, thanks to the answer by Ole.}

Answer 6

If accepted solution not working for try to rename attr.xml to attrs.xml (worked for me)