Android AudioRecord - Won't Initialize 2nd time

I was able to reproduce your problem (on a Samsung phone). I added an onDestroy() method releasing the record:

@Override
public void onDestroy() { 
    super.onDestroy();
    System.out.println("OnDestroy");
    audRec.release();
}

After adding this, the audioRecord seems to initialize correctly every time the activity is started.

I had the same problem, usually the audRec.release() helps indeed, but if you need to stop and start several times the following code is more robust. Plus, I had an issue that the recording took place in a separate thread and Android sometimes kills threads when running for a long time. So take a look at this code, it makes sure the recording is held even when the other thread is dead and upon the following audRec.start() it stops and releases:

import android.media.AudioFormat;
import android.media.AudioRecord;
import android.media.MediaRecorder; 

public class RecorderSingleton {

    private static final int FREQUENCY = 16000;

    public static RecorderSingleton instance = new RecorderSingleton();
    private AudioRecord recordInstance = null;
    private int bufferSize;

    private RecorderSingleton() {
        bufferSize = AudioRecord.getMinBufferSize(FREQUENCY, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT);
    }

    public boolean init() {
        recordInstance = new AudioRecord(MediaRecorder.AudioSource.MIC, FREQUENCY, AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, bufferSize);
        if (recordInstance.getState() == AudioRecord.STATE_UNINITIALIZED) {
            return false;
        }
        return true;
    }

    public int getBufferSize() {
        return bufferSize;
    }
    public boolean start() {
        if (recordInstance != null && recordInstance.getState() != AudioRecord.STATE_UNINITIALIZED) {
            if (recordInstance.getRecordingState() != AudioRecord.RECORDSTATE_STOPPED) {
                recordInstance.stop();
            }
            recordInstance.release();
        }
        if (!init()) {
            return false;
        }
        recordInstance.startRecording();
        return true;
    }

    public int read(short[] tempBuffer) {
        if (recordInstance == null) {
            return AudioRecord.ERROR_INVALID_OPERATION;
        }
        int ret = recordInstance.read(tempBuffer, 0, bufferSize);
        return ret;
    }

    public void stop() {
        if (recordInstance == null) {
            return;
        }
        recordInstance.stop();
        recordInstance.release();
    }
}

Then if you have a recorder thread you can use it as follows:

import android.media.AudioRecord;

public class Recorder implements Runnable {
    private int requiredSamples;
    private int takenSamples = 0;
    private boolean cancelled = false;

    public void run() {

        // We're important...
        android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_AUDIO);

        int bufferRead = 0;
        int bufferSize = RecorderSingleton.instance.getBufferSize();
        short[] tempBuffer = new short[bufferSize];
        if (!RecorderSingleton.instance.start()) {
            return;
        }
        try {
            Log.d(RoomieConstants.LOG_TAG, "Recorder Started");
            while (takenSamples < requiredSamples && !cancelled) {
                bufferRead = RecorderSingleton.instance.read(tempBuffer);
                if (bufferRead == AudioRecord.ERROR_INVALID_OPERATION) {
                    throw new IllegalStateException("read() returned AudioRecord.ERROR_INVALID_OPERATION");
                } else if (bufferRead == AudioRecord.ERROR_BAD_VALUE) {
                    throw new IllegalStateException("read() returned AudioRecord.ERROR_BAD_VALUE");
                }
                takenSamples += bufferRead;
                // do something with the samples ...
                // ...
                // ...
            }
        } finally {
            // Close resources...
            stop();
        }
    }

    public void stop() {
        RecorderSingleton.instance.stop();
    }

    public void cancel() {
        cancelled  = true;
    }
}