Android 8（Oreo）下TTF字体显示异常技术求助

Hey Martin, I’ve seen this exact issue pop up when apps jump from pre-Oreo to Android 8.0 and above—let’s break down what’s happening and how to fix it.

Why This Happens #

Android 8.0 (API 26) introduced stricter handling of custom TTF fonts, especially for non-ASCII characters. Here’s the key change:

• Pre-Oreo versions were more lenient with font character mapping, often falling back to system fonts or loading partial character sets automatically.
• Oreo enforces stricter validation of font files, so if your TTF’s symbol characters have incomplete metadata or aren’t properly mapped to their Unicode values, the system will skip rendering them and fall back to basic ASCII displays instead.

The fact that a few symbols still work tells us those specific characters have valid mappings in your font file—so we just need to fix the rest.

Step-by-Step Solutions #

1. Verify Your TTF Font’s Character Coverage #

First, confirm the problematic symbols actually exist in your font file:

• Use a tool like FontForge to open your TTF.
• Search for the Unicode values of the symbols that aren’t displaying (you can get these from your original design or by checking the ASCII fallback text).
• If the symbols are missing, you’ll need to reimport them into the font or switch to a TTF that fully supports all your required characters.

2. Update Font Loading Code #

Old Typeface.createFromAsset() calls might not play nice with Oreo’s font system. Switch to using the AndroidX FontCompat library for more reliable loading:

// Add this dependency to your build.gradle if you don't have it already:
// implementation 'androidx.core:core:1.10.0'

// Load font using FontCompat
Typeface customFont = FontCompat.createFromAsset(
    getApplicationContext().getAssets(),
    "your_font_file.ttf" // Replace with your font's path in assets
);

// Apply to your TextView/Button
yourButton.setTypeface(customFont);

This method handles font validation and character mapping more consistently across Android versions.

3. Explicitly Set Character Encoding #

While most views default to UTF-8, explicitly setting it can help eliminate edge cases:
Add this attribute to your Button/TextView in XML:

android:textEncoding="utf-8"

Or set it programmatically:

yourButton.setTextEncoding("UTF-8");

4. Test Individual Unicode Characters #

Create a simple test activity to isolate problematic symbols. For example:

// Replace \uXXXX with the Unicode value of your symbol
TextView testView = findViewById(R.id.test_view);
testView.setText("\u25A0"); // Example: black square symbol
testView.setTypeface(customFont);

If this displays correctly, the issue might be with how your app is passing the text (e.g., string encoding in resources). If not, the symbol is missing or misconfigured in the TTF.

5. Disable Font Fallback (Optional) #

If you want to force your custom font to render all characters (and avoid ASCII fallbacks), you can disable system font fallback:

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    Typeface.Builder builder = new Typeface.Builder(getAssets(), "your_font.ttf");
    builder.setFallbackFonts(null); // Disable fallback
    Typeface customFont = builder.build();
    yourButton.setTypeface(customFont);
} else {
    // Use pre-Oreo loading method
    Typeface customFont = Typeface.createFromAsset(getAssets(), "your_font.ttf");
    yourButton.setTypeface(customFont);
}

Note: This will cause missing characters to show up as empty boxes instead of ASCII, but it helps you identify exactly which symbols are missing from your font.

Final Checks #

• Make sure your font file is not corrupted—re-export it from your design tool (like Adobe Illustrator) with proper Unicode mapping.
• Clean and rebuild your project after making changes to font files or loading code.

内容的提问来源于stack exchange，提问作者Martin