Fix Android crash when setting Entry.Text in TextChanged event handler

[Copilot]

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Description

Fixes a crash on Android when modifying Entry.Text within a TextChanged event handler. The crash occurred with the error:

java.lang.IllegalArgumentException: end should be < than charSequence length
at androidx.emoji2.text.EmojiCompat.process(EmojiCompat.java:1127)
at androidx.emoji2.viewsintegration.EmojiTextWatcher.afterTextChanged(EmojiTextWatcher.java:99)

Root Cause

The issue was a race condition in EditTextExtensions.UpdateText() where SetSelection() could be called with a position exceeding the actual text length. This happened because:

1. User deletes text in an Entry, making it empty
2. TextChanged event fires with the empty text
3. Event handler sets Text = "0" to provide a default value
4. Meanwhile, Android's EmojiCompat text watcher is still processing the deletion with the old text length
5. When SetSelection() is called, the text length has changed, causing an out-of-bounds error

Changes

Added defensive bounds checking to all SetSelection() calls in EditTextExtensions.cs:

• UpdateText(EditText, IEntry) - Entry text updates
• UpdateText(EditText, IEditor) - Editor text updates
• SetInputType() - Cursor position restoration after input type changes

The fix uses Math.Min() to ensure the selection position never exceeds the current text length:

int selectionPosition = Math.Min(editText.Text?.Length ?? 0, editText.Length());
editText.SetSelection(selectionPosition);

Testing

Added UI test case that reproduces the original crash scenario:

• Entry with numeric keyboard and initial text "0"
• TextChanged handler that sets text to "0" when empty
• Test clears the Entry and verifies no crash occurs

Issues Fixed

Fixes android crash when setting Entry.Text in TextChanged event handler (related to EmojiCompat bounds checking)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>end should be < than charSequence length</issue_title>
<issue_description>### Description

I am getting a crash when using TextChanged on a Entry modifying the value.

Steps to Reproduce

1. Create a new .net Maui App
2. Add to the MainPage.xaml

            <Entry x:Name="CartonsEntry" Grid.Column="1" HorizontalOptions="Fill" Text="0" Keyboard="Numeric" TextChanged="Quantity_TextChanged" />

3. Add to the code behind

        private void Quantity_TextChanged(object sender, TextChangedEventArgs e)
        {
            if (string.IsNullOrEmpty(e.NewTextValue))
            {
                ((Entry)sender).Text = "0";
            }
        }

4. Run app
5. Delete the contents of the entry box
6. Fatal error

Link to public reproduction project repository

https://github.com/jdarwood007/MauiApp9

Version with bug

9.0.110 SR11

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

Unknown/Other

Affected platforms

Android

Affected platform versions

Android 14

Did you find any workaround?

The problem seems to be entirely calling this:

                ((Entry)sender).Text = "0";

Relevant log output

[MessageQueue-JNI] Exception in MessageQueue callback: handleReceiveCallback

[MessageQueue-JNI] java.lang.IllegalArgumentException: end should be < than charSequence length

[MessageQueue-JNI] 	at androidx.core.util.Preconditions.checkArgument(Preconditions.java:52)

[MessageQueue-JNI] 	at androidx.emoji2.text.EmojiCompat.process(EmojiCompat.java:1127)

[MessageQueue-JNI] 	at androidx.emoji2.viewsintegration.EmojiTextWatcher.afterTextChanged(EmojiTextWatcher.java:99)

[MessageQueue-JNI] 	at android.widget.TextView.sendAfterTextChanged(TextView.java:12365)

[MessageQueue-JNI] 	at android.widget.TextView$ChangeWatcher.afterTextChanged(TextView.java:15851)

[MessageQueue-JNI] 	at android.text.SpannableStringBuilder.sendAfterTextChanged(SpannableStringBuilder.java:1278)

[MessageQueue-JNI] 	at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:578)

[MessageQueue-JNI] 	at androidx.emoji2.text.SpannableBuilder.replace(SpannableBuilder.java:308)

[MessageQueue-JNI] 	at android.text.SpannableStringBuilder.delete(SpannableStringBuilder.java:231)

[MessageQueue-JNI] 	at androidx.emoji2.text.SpannableBuilder.delete(SpannableBuilder.java:330)

[MessageQueue-JNI] 	at androidx.emoji2.text.SpannableBuilder.delete(SpannableBuilder.java:48)

[MessageQueue-JNI] 	at android.text.method.BaseKeyListener.backspaceOrForwardDelete(BaseKeyListener.java:372)

[MessageQueue-JNI] 	at android.text.method.BaseKeyListener.backspace(BaseKeyListener.java:71)

[MessageQueue-JNI] 	at android.text.method.BaseKeyListener.onKeyDown(BaseKeyListener.java:498)

[MessageQueue-JNI] 	at android.text.method.NumberKeyListener.onKeyDown(NumberKeyListener.java:146)

[MessageQueue-JNI] 	at android.widget.TextView.doKeyDown(TextView.java:9511)

[MessageQueue-JNI] 	at android.widget.TextView.onKeyDown(TextView.java:9283)

[MessageQueue-JNI] 	at android.view.KeyEvent.dispatch(KeyEvent.java:2928)

[MessageQueue-JNI] 	at android.view.View.dispatchKeyEvent(View.java:15591)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at androidx.core.widget.NestedScrollView.dispatchKeyEvent(NestedScrollView.java:688)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at androidx.recyclerview.widget.RecyclerView.dispatchKeyEvent(RecyclerView.java:1981)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at androidx.coordinatorlayout.widget.CoordinatorLayout.dispatchKeyEvent(CoordinatorLayout.java:1946)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1966)

[MessageQueue-JNI] 	at android.view.ViewGroup.dispatchKeyEvent(ViewGrou...

</details>

Fixes dotnet/maui#32004

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[jsuarezruiz]

/azp run

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[jsuarezruiz]

The fix mentions EmojiCompat in comments. Consider testing with multi-codepoint emoji sequences like 👨‍👩‍👧‍👦 to ensure Length() handles them correctly.

[jsuarezruiz]

The pattern Math.Min(editText.Text?.Length ?? 0, editText.Length()) can be simplified. If Text is null, ?? 0 will always result in Min(0, x) = 0, which is correct but verbose.

[jsuarezruiz]

The test verifies the app doesn't crash and text is correct, but doesn't validate cursor position. After clearing and setting text to "0", the cursor should be at position 1 (end of text).