How to select different audio channel and access that channel audio sample by the AudioDeviceManager class?

Hi everyone,
I want to use the AudioDeviceManager to detect the audio device and select specific channel to access that channel’s audio sample. Now the problem is that how should write the code in the void MainComponent::getNextAudioBlock (const AudioSourceChannelInfo& bufferToFill) function. when i select specific channel the function could process that channel’s audio sample?

Best Regards!