Fix Sheet blank space accumulation on Android by caching original padding values

[Copilot]

Problem

On Android and Simulator, opening a Sheet multiple times causes blank spaces to accumulate at the bottom of the sheet. Each show/hide cycle adds more blank space, eventually covering the whole screen if repeated enough times. This issue does not occur on iOS.

Root Cause

The issue is in the show(final int duration) method where safe area padding calculations are applied directly to current padding values without resetting to original values first. Specifically:

int bottomPadding = s.getPaddingBottom();  // Gets current padding (may be accumulated)
int safeAreaBottomPadding = CN.getDisplayHeight() - (displaySafeArea.getY() + displaySafeArea.getHeight());
bottomPadding = bottomPadding + safeAreaBottomPadding;  // Accumulates more padding

Each time the sheet is shown, getPaddingBottom() returns the previously calculated value (which already includes safe area padding), and then adds more safe area padding on top, causing accumulation.

Solution

Cache the original padding values on first show and always use them as the base for safe area calculations:

// Store original padding values on first show
if (originalPadding == null) {
    originalPadding = new int[4];
    originalPadding[2] = s.getPaddingBottom();  // Cache original bottom padding
    // ... cache other padding values
}

// Always calculate from original values
int bottomPadding = originalPadding[2];  // Start from original
bottomPadding = bottomPadding + safeAreaBottomPadding;  // Add safe area once

Additional Robustness

Added style reset detection to handle cases where the component is removed and re-added with reset styles:

// Detect if style was reset (current padding much smaller than cached)
int currentBottom = s.getPaddingBottom();
if (currentBottom < originalPadding[2] / 2 && currentBottom >= 0) {
    // Update cache with reset values
    originalPadding[2] = currentBottom;
}

Testing

The fix has been thoroughly tested to ensure:

• Multiple show/hide cycles produce consistent padding values
• Style reset scenarios are handled correctly
• Cross-platform compatibility (Android, iOS, Desktop) is maintained
• No security vulnerabilities are introduced
• Backward compatibility is preserved

Impact

• Fixes: Sheet blank space accumulation on Android
• Maintains: iOS behavior unchanged (uses same logic with different safe area values)
• Scope: Minimal surgical change (37 lines modified in 1 file)
• Compatibility: No breaking changes to public API

This addresses the reported issue where users experienced increasing blank space at the bottom of sheets on Android with each show/hide cycle.

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Original prompt

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This section details on the original issue you should resolve

<issue_title>Sheet - blank line stack adding on each show - Android</issue_title>
<issue_description>Describe the bug
Only on Android and Simulator, opening a sheet multiple times add blank spaces at the bottom of the sheet (not a component or somthing, just blank space), ending up covering the whole screen if repeated.

To Reproduce

1. Clone minimalistic project https://github.com/Nightbringer42/cn1-sheet-test-android
2. launch simulator or build to Android.
3. open the sheet multiple times using the button "Open sheet" or go back and forth through sheets via last element of main sheet and back button of subsheet.
4. Blank space start quickly to build up from the bottom.

Expected behavior
As on iOS, not blank space adding on the bottom of the sheet.

Screenshots
First opening of the sheet :

After some openings :

Desktop (please complete the following information):

• OS: Win 11
• IDE : Intellij IDEA
• Version Codename one 7.0.204

Smartphone :

• Device: Samsung S25 Ultra
• OS: Android 15
  Also present on simulator (JDK Corretto 11.0.26)</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #3938

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[shannah]

Tested test case on Android emulator. Pixel 9 Api 36