fix: out of memory when open large file on android

[vigov5]

The PR content was generated by AI.

fix: work around file_selector_android OOM on large file picks

Problem

Picking a large file (≥ ~195 MB) on Android crashes with:

java.lang.OutOfMemoryError: Failed to allocate a 205235072 byte allocation
  at java.io.ByteArrayOutputStream.grow(ByteArrayOutputStream.java:120)
  at io.flutter.plugin.common.StandardMessageCodec.writeValue(...)
  at dev.flutter.packages.file_selector_android.GeneratedFileSelectorApi$PigeonCodec.writeValue(...)

Root cause: file_selector_android ≤ 0.5.2+6 reads the entire picked file into a ByteArrayOutputStream on the Java side and encodes it as a raw byte array through Flutter's StandardMessageCodec platform channel. For files larger than a few hundred MB this exhausts Android's heap before any Dart code runs.

An upstream fix has been proposed (flutter/flutter#141002) that would change the Java side to skip the byte read when a cache path is already available, and change the Dart side to prefer XFile(path) over XFile.fromData(bytes). However, the proposed Dart-only snippet is insufficient on its own — the OOM occurs on the Java side before the channel message is delivered to Dart, so both halves must ship together. No fixed release is available yet.

Solution

Bypass file_selector_android for pickFiles on Android using a direct MethodChannel implementation inside the app that never puts file bytes on the platform channel.

Flow:

1. MainActivity registers a MethodChannel (com.example.drift/file_picker)
2. On pickFiles, opens Intent.ACTION_OPEN_DOCUMENT (system file picker, multi-select)
3. In onActivityResult, streams each content URI to cacheDir/drift_picked/ in 64 KB chunks via InputStream.copyTo() — no large heap allocation
4. Returns only the resulting file-system paths to Dart
5. On the Dart side, SendSelectionPicker.pickFiles() detects Platform.isAndroid and delegates to AndroidFilePicker; all other platforms continue using file_selector unchanged

Files changed

File	Change
android/app/src/main/kotlin/…/MainActivity.kt	Added MethodChannel handler with Intent.ACTION_OPEN_DOCUMENT, streaming copy to cache, filename resolution via OpenableColumns
lib/platform/android_file_picker.dart	New Dart wrapper calling the channel
lib/features/send/application/send_selection_picker.dart	Android branch delegates to AndroidFilePicker; non-Android path unchanged

Future cleanup

Once a fully patched file_selector_android (both Java and Dart sides) is published, the Platform.isAndroid branch in send_selection_picker.dart, android_file_picker.dart, and the MainActivity channel can all be removed and the code reverted to using openFiles() directly.

[vsamarth]

Thanks a lot! Works for me as well