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Checking for Supported Sensor Data Fields

This topic describes how to verify that a sensor can provide a particular set of data fields.

After you have retrieved a sensor object, you can call ISensor::GetSupportedDataFields to determine whether the sensor can provide the data you need.

The following example code creates a helper function that tests whether the sensor can provide all three of the sample data fields. The function takes a pointer to a sensor as its input and returns a Boolean value, where TRUE indicates that the sensor can provide all the data fields required.


BOOL CheckForSupportedDataFields(ISensor* pSensor)
{
    assert(pSensor);

    HRESULT hr = S_OK;
    DWORD cKeys = 0; // Key count.
    BOOL bRet = FALSE;

    IPortableDeviceKeyCollection* pKeys = NULL; // Output

    // CoCreate a key collection to store property keys.
    hr = CoCreateInstance(CLSID_PortableDeviceKeyCollection, 
                                NULL, 
                                CLSCTX_INPROC_SERVER, 
                                IID_PPV_ARGS(&pKeys));

    if(SUCCEEDED(hr))
    {
        hr = pSensor->GetSupportedDataFields(&pKeys);
    }

    if(SUCCEEDED(hr))
    {
        hr = pKeys->GetCount(&cKeys);
    }

    if(SUCCEEDED(hr))
    {
        PROPERTYKEY pk;
        BOOL bHour, bMinute, bSecond = FALSE;

        for (DWORD i = 0; i < cKeys; i++)
        {
            hr = pKeys->GetAt(i, &pk);

            if(SUCCEEDED(hr))
            {
                // Test for the data fields.
                if(IsEqualPropertyKey(pk, SAMPLE_SENSOR_DATA_TYPE_HOUR))
                {
                    bHour = TRUE;
                }
                else if(IsEqualPropertyKey(pk, SAMPLE_SENSOR_DATA_TYPE_MINUTE))
                {
                    bMinute = TRUE;
                }
                else if(IsEqualPropertyKey(pk, SAMPLE_SENSOR_DATA_TYPE_SECOND))
                {
                    bSecond = TRUE;
                }
            }
        }

        // Compute the return value.
        // If all three properties were found,
        // bRet will resolve to TRUE.
        bRet = bHour && bMinute && bSecond;
    }

    SafeRelease(&pKeys);

    return bRet;
}


Related topics

ISensorDataReport

 

 

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