How to change text in TextView Android: from XML to code

Development of user interfaces for the operating system Android is impossible without using basic information display components. One of the key elements is TextView a widget designed to display static or dynamic text content on the device screen. Novice developers are often faced with the task of changing the contents of this field while the application is running, and not just at the layout stage.

There are several approaches to solving this problem, each of which has its own use cases. You can set the text directly in the markup file layout.xml or change it programmatically inside the activity or fragment using the language Kotlin or Java. Understanding the differences between these methods is critical to creating flexible and responsive applications.

In this article, we will take a closer look at all the available ways to change text, consider working with string resources, formatting, and handling errors that may occur when trying to update the interface from a background thread. We will pay special attention to performance and best practices adopted in the development community Android.

Basic setting of text in an XML markup file

The simplest and most common way to set the value of a text field is to use an attribute android:text in the layout file. This method is ideal for static titles, input field labels, or instructions that do not change during the life of the screen.

However, professional development requires adherence to the principle of separation of code and resources. Instead of writing strings directly into XML, you should use string resource references. This allows you to easily support localization of the application and change texts without recompiling the code.

To do this, a file res/values a file is being created or edited strings.xml, where the necessary string constants are declared. Then in the layout you refer to them using the syntax @string/resource_name. This approach makes the code cleaner and simplifies the work of translators.

• 📝 Direct text indication is convenient for quick interface prototyping.
• 🌍 The use of string resources is mandatory to prepare the application for multilingualism.
• ⚡ Link to the resource saves memory, since strings are loaded by the system as needed.

⚠️ Attention: Never hardcode texts in different languages directly in code or XML if you plan to publish an application on Google Play. This will complicate support and may lead to rejection by moderation for lack of localization.

Programmatically changing text through the setText method

Dynamic updating of the interface is what makes the application alive. To change the content TextView during app execution, the setTextmethod is used. Before calling this method, you must obtain a reference to the widget using findViewById or data binding mechanisms, such as ViewBinding.

Method setText has several overloads, which gives flexibility in managing content. You can pass there a regular string (String), a string resource (@string) or even an object CharSequence. It is important to understand what type of data you are passing to avoid unexpected behavior.

If you pass an integer to a method that is not a resource identifier, the application will crash with an error Resources$NotFoundException. The system will try to find a line with this ID in the resources, and if it doesn’t find it, it will crash. Therefore, to display numbers, you always need to first convert them to a string.

val textView: TextView = findViewById(R.id.myTextView)
val count = 42
// Correct: converting to a string
textView.text = count.toString
// Or using a resource
textView.setText(R.string.hello_world)

Using ViewBinding or DataBinding makes the code safer and more readable, eliminating the need for constant checks and calls. This is a modern standard for development under null and challenges findViewById. This is a modern development standard for Androidwhich is recommended to be implemented in all new projects.

Working with text formatting and styles

Often you need to not only replace text, but also highlight part of a word in bold, change the color, or add a link. For these purposes, there is a class Android there is a class SpannableString and its implementation. It allows you to apply styles to specific ranges of characters within one line.

You can combine different spans: StyleSpan for style, ForegroundColorSpan for color, URLSpan for clickable links. This gives you complete control over typography without having to create many separate widgets TextView.

It is also possible to use HTML markup via the Html.fromHtmlmethod. Although this approach is less productive than working with spans, it greatly simplifies the task if the text comes from the server already in HTML format or contains complex structures.

Span type	Description	Use example
StyleSpan	Changes the style (bold, italics)	Typeface.BOLD
ForegroundColorSpan	Changes the color of the text	Color.RED
URLSpan	Make the text a clickable link	"https://..."
StrikethroughSpan	Adds a strikethrough	For discounts or removed items

When working with formatting, it is important to keep performance in mind. Creating complex objects Spannable in a loop or in a onBindViewHolder list method can lead to slow scrolling. In such cases, it is better to cache formatted strings or use simple resources.

How to make part of the text bold?

val text ="Regular and BOLD text"

val spannable = SpannableString(text)

spannable.setSpan(StyleSpan(Typeface.BOLD), 12, 17, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE)

textView.text = spannable

Updating text from a background thread

One of the most common mistakes newbies make is trying to change the text in TextView from a thread other than the main one (UI Thread). In Android there is a strict rule: any manipulation of interface elements must occur only in the main application thread.

If you are performing a network request, database read, or complex calculation in a background thread, directly passing the result to textView.text = result will cause an exception CalledFromWrongThreadException. The application will immediately stop and the user will see an error screen.

To safely update the interface, you must switch to the main thread. In modern Kotlin coroutines with a dispatcher are used for this. Dispatchers.Main. In the classic approach, you can use runOnUiThread or Handler, tied to the main looper.

⚠️ Attention: Ignoring interface thread safety rules is the main reason for unstable applications. Always check which thread is running the UI update code.

Using architectural components such as LiveData or StateFlowautomatically solves this problem. These tools are observable and ensure that interface updates occur in the correct flow as soon as data changes.

Optimizing and searching widgets

Application performance directly depends on how you find and cache references to interface elements. Frequent calling findViewById inside loops or methods that are called repeatedly (for example, when scrolling a list) negatively affects the speed of work.

The best practice is to search for the view once when creating an activity or fragment and store the reference in a variable. An even more effective solution is to switch to ViewBinding. This tool generates a class for each XML file, providing type-safe access to all elements. Eliminates the possibility of errors since type checking occurs at compile time. It is also faster than manually searching by ID because it does not use reflection.

ViewBinding eliminates the possibility of error ClassCastException And NullPointerException, since type checking occurs at the compilation stage. In addition, it works faster than manual search by ID, since it does not use reflection.

If you are forced to use the old approach with findViewById, make sure that the variable type is specified explicitly and matches the type in the XML. Errors in types (for example, expect TextView, and in layout Button) will lead to a crash at startup.

• 🚀 ViewBinding is a modern standard that speeds up the development and operation of the application.
• 🛑 Avoid calling findViewById inside methods onDraw or list adapters.
• 🧩 Use DataBindingif the display logic is complex and requires two-way communication.

Common errors and ways to solve them

Even experienced developers sometimes encounter problems when working with text fields. The most insidious mistake is passing the wrong resource to setText(int). The compiler will not warn you if you accidentally pass a numeric value instead of a resource ID, but the application will crash during execution.

Another common problem involves encoding and special characters. If the text is downloaded from the network or a file, make sure that it is correctly decoded in UTF-8. Invalid characters may appear as squares or question marks.

It is also worth remembering the text length limit. Although TextView can render large amounts of data, this can lead to issues with rendering performance (lag) and memory consumption. For long texts, use the android:maxLines attribute or implement the "show more" mechanism.

⚠️ Attention: Android interfaces and APIs are constantly updated. Methods that are current in one version of the SDK may be marked as deprecated (@Deprecated) in another. Always check the documentation for your target API version.

Why the application crashes with the error Resources$NotFoundException setText?

This happens when you pass an setText integer number (int) to the method, which the system interprets as a resource ID rather than as text. For example, textView.setText(100) will cause a crash, since the resource with ID 100 does not exist. To display a number, use textView.setText(100.toString) or textView.text = 100.toString.

How to change text in a TextView from another class or thread?

Direct modification from another thread is prohibited. You need to pass data to the Activity or Fragment through the Callback interface or EventBus. UI updating should only happen inside the component's lifecycle method on the main thread. LiveData, BroadcastReceiver or bus events (EventBus). UI updating should only happen inside the component's lifecycle method on the main thread.

What is the difference between setText and text = in Kotlin?

Functionally there is no difference. text ="..." in Kotlin it is a wrapper property that internally calls the method setText. Using a property is preferable because the code becomes more concise and reads like a natural value assignment.

Can you use HTML tags in TextView?

Yes, TextView supports basic HTML markup. To do this, use the Html.fromHtml(string, flags)method. Tags , , , , , and others are supported. However, complex layout via HTML is not recommended due to possible differences in rendering on different devices.How to make text clickable without using a Button?Set the attributein XML to automatically recognize links, phone numbers and addresses. Or programmatically useito create custom clickable sections of text inside regular textBasic text settings in an XML markup fileProgrammatically changing text using the setText methodWorking with formatting and text stylesUpdating text from a background threadOptimizing and searching for widgetsCommon errors and ways to solve themWhere to find downloads in Samsung A12: a complete guide to foldersHow to enable dark mode in TikTok on Android: instructionsHow to display a document shortcut on the Android desktopWhy do you need a launcher on Android: functions, settings and the best solutionsHow to add a Yandex widget to the Android home screen: instructionsWhere to find downloads on Samsung A12: a complete guide to foldersFind out where to find downloads on Samsung A12. Detailed instructions for working with the file manager, veryHow to enable dark mode in TikTok on Android: instructionsA complete guide to activating the night theme in TikTok on Android. Setting up system parameters, slaveHow to display a document shortcut on the Android desktopFull instructions: how to add PDF, Word and other files to the main screen of your phone. Setting up a widgetWhy do you need a launcher on Android: functions, settings and the best solutionsFind out why you need a launcher on Android. A complete guide to changing the interface, optimizing the system, customHow to add a Yandex widget to the Android home screen: instructionsDetailed instructions for installing Yandex widgets on your phone screen. Solving problems with disappearanceVoice dialing on Android: how to enable and configure | Full guideFind out how to enable and configure voice typing on Android. Complete guide to Gboard and Google Ac🤖 Android GuideComplete guide to setting up, repairing and optimizing smartphones based on Android.SectionsInformationAll sectionsSite mapNavigation🔍 Search for articles...Learn how to programmatically and via XML change text in TextView Android. setText methods, resources, Spannable and solutions to common errors.How to change text in TextView Android: a complete guideLearn how to change text in TextView Android programmatically and via XML. setText methods, resources, Spannable and solutions to common errors.

How to make text clickable without using a Button?

Set the attribute android:autoLink="all" in XML to automatically recognize links, phone numbers and addresses. Or programmatically use LinkMovementMethod i URLSpan to create custom clickable sections of text inside regular text TextView.