Android判断麦克风是否被占用

返回true就是没有被占用。
返回false就是被占用。
代码来源：
https://stackoverflow.com/questions/35633513/how-to-check-whether-microphone-is-used-by-any-background-app

private boolean validateMicAvailability(){
    Boolean available = true;
    AudioRecord recorder =
            new AudioRecord(MediaRecorder.AudioSource.MIC, 44100,
                    AudioFormat.CHANNEL_IN_MONO,
                    AudioFormat.ENCODING_DEFAULT, 44100);
    try{
        if(recorder.getRecordingState() != AudioRecord.RECORDSTATE_STOPPED ){
            available = false;

        }

        recorder.startRecording();
        if(recorder.getRecordingState() != AudioRecord.RECORDSTATE_RECORDING){
            recorder.stop();
            available = false;

        }
        recorder.stop();
    } finally{
        recorder.release();
        recorder = null;
    }

    return available;
}