Material design recommends using a dynamic type text instead of smaller type sizes or truncating large size text. Android making this much easier to implement with the introduction of TextView auto-sizing. With Android O and Support Library 26.0+, TextView gains a new property auto-size text type which allows you to optimize the text size when working with dynamic content.

Adding support library dependency

The Support Library provides full support to the auto sizing TextView feature on devices running Android versions prior to Android 8.0 (API level 26). The android.support.v4.widget package contains the TextViewCompat class to access features in a backward-compatible fashion. Support Library 26 has now been moved to Google’s maven repository, first include that in your project level build.gradle.

buildscript {
   repositories {
       google()
   }
   ....
}

Add the support library in your app level build.gradle.

dependencies {
   ....
   implementation 'com.android.support:support-v4:26.0.2'
}

Enable Autosizing

To enable auto-size in XML, set autoSizeTextType to uniform.This scales the text uniformly on horizontal and vertical axes, ignoring the text size attribute.When using support Library, make sure you use the app namespace.Note that you shouldn’t use wrap_content for layout width or layout height for a textView set to auto-size since it may produce unexpected results.Instead, use match_prent or a fixedsize.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
  <TextView
      android:layout_width="match_parent"
      android:layout_height="200dp"
      app:autoSizeTextType="uniform" />
</LinearLayout>

Turn off auto-sizing by selecting none instead of uniform. You can also use auto-size programmatically like this.

TextViewCompat.setAutoSizeTextTypeWithDefaults(TextView textview, int autoSizeTextType)

Provide an instance of the TextView widget and one of the text types, such asTextViewCompat.AUTO_SIZE_TEXT_TYPE_NONE or TextViewCompat.AUTO_SIZE_TEXT_TYPE_UNIFORM.

Customize TextView

If you want to customize your TextView more, it has some extra attributes for you to auto-size min and max text size and step granularity.The TextView will scale uniformly in the range between the minimum and the maximum size in increments of step granularity.If you don’t set these properties, the default values will be used. To define a range of text sizes and a dimension in XML, use the app namespace and set the following attributes:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
  <TextView
      android:layout_width="match_parent"
      android:layout_height="200dp"
      app:autoSizeTextType="uniform"
      app:autoSizeMinTextSize="12sp"
      app:autoSizeMaxTextSize="100sp"
      app:autoSizeStepGranularity="2sp" />
</LinearLayout>

To define a range of text sizes and a dimension programmatically, call the setAutoSizeTextTypeUniformWithConfiguration(int autoSizeMinTextSize, int autoSizeMaxTextSize, int autoSizeStepGranularity, int unit) method. Provide the maximum value, the minimum value, the granularity value, and any TypedValue dimension unit.

Preset Sizes

To have more control over the final size, for example, your app needs to comply with specific text size design guidelines, you can provide a list of size, and it will use the largest one that fits. Create an array with the size in your resources and then set the auto-size present sizes attribute in the XML.

<resources>
  <array name="autosize_text_sizes">
    <item>10sp</item>
    <item>12sp</item>
    <item>20sp</item>
    <item>40sp</item>
    <item>100sp</item>
  </array>
</resources>
<TextView
    android:layout_width="match_parent"
    android:layout_height="200dp"
    android:autoSizeTextType="uniform"
    app:autoSizePresetSizes="@array/autosize_text_sizes" />

To use preset sizes to set up the auto-sizing of TextView programmatically through the support library, call theTextViewCompat.setAutoSizeTextTypeUniformWithPresetSizes(TextView textView, int[] presetSizes, int unit) method. Provide an instance of the TextView class, an array of sizes, and any TypedValue dimension unit for the size.

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