如何在样式文件中设置Android Support AutoSize TextView？

Great question! I've run into this exact issue before when trying to standardize auto-sizing across an app without repeating layout code. The key thing to remember is that while you use the app: prefix for these attributes in XML layouts, you don't need the prefix in styles—you can reference the raw attribute names defined by the AppCompat library directly.

Here's a step-by-step solution:

1. Ensure You're Using AppCompat Widgets #

First, make sure all your TextViews are actually AppCompatTextView (or subclasses like AppCompatButton). The native Android TextView doesn't support the AppCompat auto-sizing features, so this is non-negotiable. You can either:

• Explicitly use <android.support.v7.widget.AppCompatTextView> in your layouts, or
• Let the AppCompat library inflate them automatically (if your app uses an AppCompat theme, this happens by default for most standard widgets).

2. Define Your Auto-Sizing Style #

In your res/values/styles.xml, create a style that uses the AppCompat auto-sizing attributes without the app: prefix. These attributes are defined in the AppCompat library's attrs.xml, so they're available directly in styles:

<style name="AutoSizeTextStyle" parent="TextAppearance.AppCompat">
    <!-- Enable uniform auto-sizing (supports "none" or "uniform") -->
    <item name="autoSizeTextType">uniform</item>
    <!-- Minimum text size -->
    <item name="autoSizeMinTextSize">12sp</item>
    <!-- Maximum text size -->
    <item name="autoSizeMaxTextSize">24sp</item>
    <!-- Step size for text size adjustments -->
    <item name="autoSizeStepGranularity">2sp</item>
    <!-- Optional: Use preset sizes instead of min/max/step -->
    <!-- <item name="autoSizePresetSizes">@array/autosize_text_sizes</item> -->
</style>

If you prefer using preset sizes instead of a range, define an array in res/values/arrays.xml:

<array name="autosize_text_sizes">
    <item>12sp</item>
    <item>16sp</item>
    <item>20sp</item>
    <item>24sp</item>
</array>

3. Apply the Style #

You can apply this style to individual widgets:

<android.support.v7.widget.AppCompatTextView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="This text will auto-size!"
    style="@style/AutoSizeTextStyle" />

Or, to apply it globally to all text widgets in your app, add it to your app's theme:

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
    <!-- Other theme attributes -->
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
    
    <!-- Apply auto-sizing to all text views -->
    <item name="textAppearance">@style/AutoSizeTextStyle</item>
    <!-- For buttons specifically, use: -->
    <!-- <item name="buttonTextAppearance">@style/AutoSizeTextStyle</item> -->
</style>

Key Notes #

• Dependency Check: Make sure your build.gradle (Module level) includes the AppCompat library (version 26.0.0 or higher, since auto-sizing was added then):

  dependencies {
      implementation 'com.android.support:appcompat-v7:28.0.0'
      // For AndroidX, use: implementation 'androidx.appcompat:appcompat:1.6.1'
  }
  

• Avoid mixing fixed android:textSize with auto-sizing: If you set a fixed text size in your style, the auto-sizing system will still override it based on your min/max/step settings, but it's cleaner to omit fixed sizes when using auto-sizing.

内容的提问来源于stack exchange，提问作者Jose M Lechon