Description

Fixes a crash that occurs when an Entry is bound to a float value with fractional string formatting (e.g., {0:F2}) on Android devices with EmojiCompat enabled.

Problem

When users type in an Entry bound to a float with StringFormat='{}{0:F2}', the app crashes with:

Java.Lang.IllegalArgumentException: 'end should be < than charSequence length'

Root Cause: When a user types "1", the StringFormat converts it to "1.00", changing the text length from 1 to 4 characters. EmojiCompat gets confused about cursor positioning when SetTextKeepState() is called with the new text length, causing the crash.

Reproduction:

<Entry Text="{Binding FloatValue, StringFormat='{}{0:F2}'}" />

1. Clear the entry field completely
2. Type a number (e.g., "1", "3.5")
3. App crashes on physical Android devices

Solution

Added a try-catch block around SetTextKeepState() in the UpdateTextFromPlatform() method:

• Normal case: SetTextKeepState() works as before, preserving cursor position
• EmojiCompat crash case: Falls back to regular setText() with manual cursor positioning

try
{
    editText.SetTextKeepState(newText);
}
catch (Java.Lang.IllegalArgumentException)
{
    // Fallback to regular setText with manual cursor positioning
    var cursorPosition = editText.SelectionStart;
    editText.Text = newText;
    var newCursorPosition = System.Math.Min(cursorPosition, newText?.Length ?? 0);
    if (newCursorPosition <= editText.Text?.Length)
    {
        editText.SetSelection(newCursorPosition);
    }
}

Benefits

• ✅ Prevents the crash - No more IllegalArgumentException
• ✅ Minimal impact - Only affects the specific problematic scenario
• ✅ Works for Entry and Editor - Both controls use the same code path
• ✅ Preserves functionality - Maintains cursor positioning when possible
• ✅ No breaking changes - Existing behavior unchanged in normal cases

Testing

Added comprehensive test case Issue25728:

• UI reproduction page for manual testing
• Automated tests verifying no crashes when typing numbers with StringFormat
• Edge case coverage: decimals, zero, programmatic value changes

Microsoft Docs

• Related Google issue
• Entry control documentation

Fixes #25728.

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