Reading accelerometer data with watchOS2 - iOS9 - XCode 7.0

Question

I'm trying to record and read historical data from the Apple Watch. Unfortunately, associated DataList is always equal to nil.

To be more explicit, on my watch app, I got two buttons: - one to start recording the data - one to read the data

Here is the associated code - running on the WatchKit Extension:

- (IBAction)start {

    // Check authorizations with boolean
    bool toTest_AccelerometerAvailable = [CMSensorRecorder isAccelerometerRecordingAvailable];
    bool toTest_RecordingAuthorized = [CMSensorRecorder isAuthorizedForRecording];

    // Check if recorder has been initialized, then launch record session for 20 seconds
    if ([CMSensorRecorder isAuthorizedForRecording]) {
        if (!self.recorder)
        {
            self.recorder = [[CMSensorRecorder alloc] init];
        }

        NSTimeInterval interval = 1 * 20;
        [self.recorder recordAccelerometerFor:interval];
    }
}

- (IBAction)read {

    // Check authorizations with boolean
    bool toTest_AccelerometerAvailable = [CMSensorRecorder isAccelerometerRecordingAvailable];
    bool toTest_RecordingAuthorized = [CMSensorRecorder isAuthorizedForRecording];

    // Try to get historical data from the last 2 days
    NSDate *now = [NSDate date];
    NSDate *startDate = [now dateByAddingTimeInterval:-2*24*60*60];
    CMSensorDataList *dataList = [self.recorder accelerometerDataFrom:startDate to:[NSDate date]];
}

On the iOS app side, I asked for the form & fitness authorization.

Debug session gave the following results:

• boolean toTest_RecordingAuthorized is always equal to true (start & read function) - access to form & fitness was asked in associated iOS app.

• boolean toTest_AccelerometerAvailable is always equal to false (start & read function)

• CMSensorDataList *dataList is equal to nil at any time

Tests were made with simulators but also with real devices (iOS 9.0 & watchOS 2.0). Same result!

I guess, as long as isAccelerometerRecordingAvailable returns false, the problem will persist. No idea how to fix it...

Does anyone also experiment this problem and fix it?

Answer 1

-2*24*60*60 , You are trying to access last 2 days of data, but according to documentation you can only query 12 hours of data. Read it here: Apple Documentation about CMSensorRecorder