How to make text bold in Android Studio: a complete guide for developers

Working with text in Android applications requires not only functionality, but also correct visual design. Bold font is one of the key tools for focusing the user's attention on important interface elements: headings, buttons, warnings or highlighted fragments. However, this can be implemented in several ways - from a simple XML style to programmatic control via Android Studio This can be implemented in several ways - from a simple XML style to programmatic control via Kotlin or Java.

In this article we will analyze all the current methods, including the nuances of working with TextView, SpannableString, styles Material Design and even formatting in strings.xml. We will pay special attention to cross-platform solutions (for example, for Jetpack Compose) and typical errors that lead to incorrect display of text on different versions Android. If you are looking for a way to highlight text in code or layout, here you will find ready-made solutions with examples.

1. Making text bold in XML markup

The simplest and most common way is to use the attribute android:textStyle in the markup file (activity_main.xml or fragment_layout.xml). This method is suitable for static text that does not require dynamic changes at runtime.

Basic syntax example:

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="This text is bold"
android:textStyle="bold" />

To combine styles (for example, bold and italic), use the symbol |:

android:textStyle="bold|italic"

• ✅ Pros: simplicity, not requires code, supported by all versions Android.
• ❌ Cons: cannot be applied to part of the text within one TextView.

⚠️ Attention: If you use custom fonts via android:fontFamily, make sure that the selected font supports bold style. Otherwise, the attribute textStyle="bold" will not have an effect.

2. Dynamically changing text style in Kotlin/Java

When text or its formatting changes while the application is running (for example, when a button is clicked), you need to control the style programmatically. In Kotlin i Java this is done through the method setTypeface() with flag Typeface.BOLD.

Example on Kotlin:

val textView = findViewById<TextView>(R.id.my_text_view)
textView.setTypeface(null, Typeface.BOLD)

For Java the syntax is similar:

TextView textView = findViewById(R.id.my_text_view);
textView.setTypeface(null, Typeface.BOLD);

• 🔹 Tip 1: The first parameter setTypeface(null, ...) resets the font family to the standard one. If you need to save a custom font, specify it explicitly: textView.typeface = ResourcesCompat.getFont(context, R.font.my_font).
• 🔹 Tip 2: To dynamically switch between bold and regular style, save the original Typeface into a variable.

Make sure that the TextView is initialized (not null)

Save the original Typeface if a rollback is required

Check font support on target versions of Android

Test on an emulator with different screen sizes-->

3. Partial text selection using SpannableString

If you need to highlight only part of the text within one TextView (for example, one word in a sentence), use the class SpannableString together with StyleSpan. This method is indispensable for working with multi-line text or formatting individual characters.

An example of highlighting the word "important" in the text:

val text = "This message is very important for the user"
val spannableString = SpannableString(text)

// Selecting the word "important" (starts from the 17th character, length 5)
spannableString.setSpan(
StyleSpan(Typeface.BOLD),
17, // start
22, // end
Spannable.SPAN_EXCLUSIVE_EXCLUSIVE
)

textView.text = spannableString

For Java replacement is minimal - use new SpannableString() i new StyleSpan(Typeface.BOLD).

⚠️ Attention: When using SpannableString on texts with emoji or special characters (for example, hieroglyphs), please count indexes start and end taking into account their length in UTF-16. For precise positioning, use text.length or libraries like ICU4J.

4. Formatting text via HTML in strings.xml

If the text is stored in resources (res/values/strings.xml), you can use HTML tags for formatting. This method is convenient for static texts that do not change at runtime, but require complex design.

Example in strings.xml:

Welcome, %s!

To display it in TextView, use Html.fromHtml():

textView.text = Html.fromHtml(getString(R.string.welcome_message, "Ivan"), Html.FROM_HTML_MODE_LEGACY)

• 📌 Important: Starting from Android N (API 24), method Html.fromHtml() requires a flag FROM_HTML_MODE_LEGACY to support tags like <b>.
• 🔧 Alternative: For projects on Kotlin you can use the extension String.htmlToSpanned() from libraries Android KTX.

<style name="BoldText">
<item name="android:textStyle">bold</item>
<item name="android:textSize">16sp</item>
<item name="android:textColor">@color/black</item>
</style>

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Styled text" />

textView.setTextAppearance(R.style.BoldText)

Text(
text = "Bold text in Compose",
fontWeight = FontWeight.Bold
)

Text(
buildAnnotatedString {
append("Plain text ")
withStyle(style = SpanStyle(fontWeight = FontWeight.Bold)) {
append("bold fragment")
}
}
)

editText.addTextChangedListener(object : TextWatcher {
override fun afterTextChanged(s: Editable?) {
val hashtagPattern = Regex("#\\w+")
s?.let {
val spans = it.getSpans(0, it.length, StyleSpan::class.java)
spans.forEach { span -> it.removeSpan(span) }

hashtagPattern.findAll(it).forEach { match ->
it.setSpan(
StyleSpan(Typeface.BOLD),
match.range.first,
match.range.last + 1,
Spanned.SPAN_EXCLUSIVE_EXCLUSIVE
)
}
}
}
// ... other TextWatcher methods
})

val title = SpannableString("New message")
title.setSpan(StyleSpan(Typeface.BOLD), 0, title.length, 0)

val builder = NotificationCompat.Builder(context, CHANNEL_ID)
.setContentTitle(title)
.setContentText("Notification text")
.setSmallIcon(R.drawable.ic_notification)

webView.loadData(
"Plain text bold text",
"text/html",
"UTF-8"
)