AndroidBackend: Switch to custom container (RelativeLayout too slow)#550
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stackotter merged 2 commits intomainfrom May 5, 2026
Merged
AndroidBackend: Switch to custom container (RelativeLayout too slow)#550stackotter merged 2 commits intomainfrom
stackotter merged 2 commits intomainfrom
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RelativeLayout's onMeasure implementation has a branching factor of 2, leading to Android's measurement pass being exponential with regard to the depth of the SwiftCrossUI view hierarchy.
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The issue with toggle buttons, switches, and checkboxes being invisible was just because those SwiftCrossUI views weren't setting the sizes of their underlying widgets. The AndroidBackend now requires that all widgets get explicitly assigned sizes, so that was causing the toggles to be rendered with a size of 0x0. |
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The hiccup on my segmented picker prototype went from over four seconds to under 8ms. I'd say that's a pretty good improvement
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RelativeLayout's onMeasure implementation has a branching factor of 2, leading to Android's measurement pass being exponential with regard to the depth of the SwiftCrossUI view hierarchy. That appears to be the cause of #545, which we found out thanks to @bbrk24's profiling earlier today.
This PR resolves the issue by switching over to a custom ViewGroup subclass for our container implementation. The new implementation is written in Kotlin because a) it's much more ergonomic interacting with Android APIs from Kotlin, and b) it reduces the number of JNI calls we have to make.
This is a draft because it seems to have broken a couple of views such as checkboxes. We may be assigning a size that is too small? I haven't looked into it yet.