debugAssertNoTransientCallbacks method
- String reason
Asserts that there are no registered transient callbacks; if there are, prints their locations and throws an exception.
A transient frame callback is one that was registered with scheduleFrameCallback.
This is expected to be called at the end of tests (the flutter_test framework does it automatically in normal cases).
Call this method when you expect there to be no transient callbacks registered, in an assert statement with a message that you want printed when a transient callback is registered:
assert(SchedulerBinding.instance.debugAssertNoTransientCallbacks(
'A leak of transient callbacks was detected while doing foo.'
));
Does nothing if asserts are disabled. Always returns true.
Implementation
bool debugAssertNoTransientCallbacks(String reason) {
assert(() {
if (transientCallbackCount > 0) {
// We cache the values so that we can produce them later
// even if the information collector is called after
// the problem has been resolved.
final int count = transientCallbackCount;
final Map<int, _FrameCallbackEntry> callbacks = Map<int, _FrameCallbackEntry>.of(_transientCallbacks);
FlutterError.reportError(FlutterErrorDetails(
exception: reason,
library: 'scheduler library',
informationCollector: () => <DiagnosticsNode>[
if (count == 1)
// TODO(jacobr): I have added an extra line break in this case.
ErrorDescription(
'There was one transient callback left. '
'The stack trace for when it was registered is as follows:',
)
else
ErrorDescription(
'There were $count transient callbacks left. '
'The stack traces for when they were registered are as follows:',
),
for (final int id in callbacks.keys)
DiagnosticsStackTrace('── callback $id ──', callbacks[id]!.debugStack, showSeparator: false),
],
));
}
return true;
}());
return true;
}