为何targetSdkVersion 30时安卓页面文本不显示，28时正常？

Hey there! I’ve run into this exact issue a few times when upgrading target SDK versions—let’s walk through the most likely reasons your text disappears on API 30 but works on API 28, plus how to fix each one:

1. Dark Mode/Color Contrast Mismatch #

Android 11 (API 30) tightened up system dark mode handling. If your TextView uses default system text colors like ?android:textColorPrimary, your app might be switching to dark mode automatically on API 30, while your background color also shifts to a dark shade—making text blend in completely. On API 28, dark mode wasn’t enforced as strictly, so colors stayed visible.

Fix:

• Either explicitly set a static text color on your TextView (e.g., android:textColor="#212121" for light text, android:textColor="#FFFFFF" for dark)
• Or properly configure your app’s themes for light/dark modes:
  • Create res/values-night/styles.xml if you don’t have it, and define contrasting text/background colors for dark mode
  • Ensure your theme inherits from a dark-mode-aware parent like Theme.MaterialComponents.DayNight

2. Custom Font Loading Failures #

API 30 introduced subtle changes to how fonts are loaded. If you’re using custom fonts stored in assets/ instead of the recommended res/font/ directory, you might hit permission or loading issues that didn’t exist on API 28.

Fix:

• Move your font files to res/font/ (create the directory if needed)
• Reference the font directly in your TextView or theme:

  <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:fontFamily="@font/your_custom_font_name"/>
  

• If you need to load fonts dynamically, use ResourcesCompat.getFont(context, R.font.your_custom_font) instead of asset-based loading.

3. Layout Constraint/Visibility Issues #

The layout engine in API 30 has minor tweaks that can break layouts that worked on older versions. Your TextView might be getting squeezed to 0x0 size, pushed off-screen, or covered by another view without you noticing.

Fix:

• Use Android Studio’s Layout Inspector (Tools > Layout Inspector) to inspect the TextView’s actual bounds and visibility status
• Double-check your ConstraintLayout constraints (if using it) to ensure the TextView has proper start/end/top/bottom constraints or a fixed size
• Verify that android:visibility is set to visible (not invisible or gone)

4. Scoped Storage Blocking Text Content #

If your text is loaded from external storage (like a text file on the SD card), API 30’s Scoped Storage restrictions will prevent your app from accessing that file unless you use the newer storage APIs. On API 28, you could still use the old READ_EXTERNAL_STORAGE permission without extra hoops.

Fix:

• For temporary compatibility (not recommended long-term), add android:requestLegacyExternalStorage="true" to your <application> tag in AndroidManifest.xml
• For a permanent solution, use MediaStore to access public files or the Storage Access Framework (SAF) to let users select files manually

5. Deprecated TextView Attributes #

Some TextView attributes changed behavior or were deprecated in API 30. For example, android:autoSizeTextType has stricter default settings, or android:textAllCaps might not apply as expected.

Fix:

• Check your TextView attributes against Android’s API 30 documentation
• Replace deprecated attributes with their modern equivalents. For auto-sizing text, ensure you set android:autoSizeMinTextSize, android:autoSizeMaxTextSize, and android:autoSizeStepGranularity explicitly if needed

If none of these fixes work, sharing your layout XML, theme configuration, or code that sets the text would help narrow down the issue further!

内容的提问来源于stack exchange，提问作者Mostafa khaled