Predictive Back Gesture animation doesn't and can't implement material design spec to match native behavior #153577
Description
Steps to reproduce
Use PredictiveBackPageTransitionsBuilder()
Expected results
The same animations and behavior as the native apps and system.
Spec: https://developer.android.com/design/ui/mobile/guides/patterns/predictive-back
Actual results
In the "pre-commit" part of the animation:
- the front page abruptly disappears when swiping across 35% of the screen
- the front and back pages ignore if the gesture started from the left or right edge
- the front and back pages don't go up and down following finger
In the "post-commit" part of the animation:
- the animation goes way too fast (<100ms, should be ~300ms)
- the animation blocks all user inputs for about 700ms after the animation is visually finished
- the animation is the same as the "pre-commit" one, which is not what happens in the rest of Android and in the spec.
1. and 6. can be worked around by writing a custom PageTransitionBuilder.
2. and 3. can be partially worked around: only for the front page.
4. and 5. cannot be worked around without editing the SDK source code itself.
Flutter Doctor output
Doctor output
flutter doctor -v devenv-shell-env
[✓] Flutter (Channel master, 3.24.0-1.0.pre.605, on NixOS 24.05 (Uakari) 6.8.12, locale en_US.UTF-8)
• Flutter version 3.24.0-1.0.pre.605 on channel master at /home/paulg/Repos/flutter
• Upstream repository https://github.com/flutter/flutter.git
• Framework revision bced008679 (14 hours ago), 2024-08-15 22:29:24 -0400
• Engine revision a8fefc8118
• Dart version 3.4.3
• DevTools version 2.38.0
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
• Android SDK at /nix/store/nzwnj7rq8a6cvzbsszf4n9zfvx101zm5-androidsdk/libexec/android-sdk
• Platform android-34, build-tools 30.0.3
• ANDROID_HOME = /nix/store/nzwnj7rq8a6cvzbsszf4n9zfvx101zm5-androidsdk/libexec/android-sdk
• ANDROID_SDK_ROOT = /nix/store/nzwnj7rq8a6cvzbsszf4n9zfvx101zm5-androidsdk/libexec/android-sdk
• Java binary at: /nix/store/l7pwy1rxdrb13svqandm720d06fycd8c-openjdk-17.0.11+9/lib/openjdk/bin/java
• Java version OpenJDK Runtime Environment (build 17.0.11+9-nixos)
• All Android licenses accepted.
[✓] Chrome - develop for the web
• CHROME_EXECUTABLE = /nix/store/cg5bvzxml5bbdw8wlrywb6q7hpdjq0ij-google-chrome-127.0.6533.88/bin/google-chrome-stable
[✓] Linux toolchain - develop for Linux desktop
• clang version 16.0.6
• cmake version 3.29.6
• ninja version 1.12.1
• pkg-config version 0.29.2
[!] Android Studio (not installed)
• Android Studio not found; download from https://developer.android.com/studio/index.html
(or visit https://flutter.dev/docs/get-started/install/linux#android-setup for detailed instructions).
[✓] Connected device (3 available)
• Pixel 7 Pro (mobile) • 192.168.1.13:43591 • android-arm64 • Android 15 (API 35)
• Linux (desktop) • linux • linux-x64 • NixOS 24.05 (Uakari) 6.8.12
• Chrome (web) • chrome • web-javascript • Google Chrome 127.0.6533.88
[✓] Network resources
• All expected network resources are available.
! Doctor found issues in 1 category.