Android MediaCodec 录制音频功能实现完整代码

以下是一个简单的 Android MediaCodec 录制音频的实现代码：

public class AudioRecorder {

    private static final String MIME_TYPE = "audio/mp4a-latm"; //音频编码格式
    private static final int SAMPLE_RATE = 44100; //采样率
    private static final int BIT_RATE = 64000; //比特率
    private static final int CHANNEL_COUNT = 1; //声道数量

    private MediaCodec mMediaCodec;
    private ByteBuffer[] mInputBuffers;
    private ByteBuffer[] mOutputBuffers;
    private MediaFormat mMediaFormat;

    private boolean mIsRecording;

    public void startRecording(String filePath) {
        try {
            mMediaCodec = MediaCodec.createEncoderByType(MIME_TYPE);
            mMediaFormat = MediaFormat.createAudioFormat(MIME_TYPE, SAMPLE_RATE, CHANNEL_COUNT);
            mMediaFormat.setInteger(MediaFormat.KEY_BIT_RATE, BIT_RATE);

            mMediaCodec.configure(mMediaFormat, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
            mMediaCodec.start();

            mInputBuffers = mMediaCodec.getInputBuffers();
            mOutputBuffers = mMediaCodec.getOutputBuffers();

            FileOutputStream fos = new FileOutputStream(filePath);
            BufferedOutputStream bos = new BufferedOutputStream(fos);

            mIsRecording = true;
            while (mIsRecording) {
                int inputBufferIndex = mMediaCodec.dequeueInputBuffer(-1);
                if (inputBufferIndex >= 0) {
                    ByteBuffer inputBuffer = mInputBuffers[inputBufferIndex];
                    inputBuffer.clear();

                    short[] buffer = null; //这里应该是通过 AudioRecord 获取到 PCM 数据
                    //将 PCM 数据写入 inputBuffer
                    for (int i = 0; i < buffer.length; i++) {
                        inputBuffer.putShort(buffer[i]);
                    }

                    mMediaCodec.queueInputBuffer(inputBufferIndex, 0, buffer.length * 2, 0, 0);

                    MediaCodec.BufferInfo bufferInfo = new MediaCodec.BufferInfo();
                    int outputBufferIndex = mMediaCodec.dequeueOutputBuffer(bufferInfo, 0);
                    while (outputBufferIndex >= 0) {
                        ByteBuffer outputBuffer = mOutputBuffers[outputBufferIndex];

                        byte[] outData = new byte[bufferInfo.size];
                        outputBuffer.get(outData);

                        bos.write(outData, 0, outData.length);
                        bos.flush();

                        mMediaCodec.releaseOutputBuffer(outputBufferIndex, false);
                        outputBufferIndex = mMediaCodec.dequeueOutputBuffer(bufferInfo, 0);
                    }
                }
            }

            mMediaCodec.stop();
            mMediaCodec.release();
            mMediaCodec = null;

            bos.flush();
            bos.close();
            fos.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void stopRecording() {
        mIsRecording = false;
    }
}

注意，该代码中的 `short[] buffer` 应该是通过 `AudioRecord` 获取到的 PCM 数据，本例未给出。同时，在实际应用中，应该在子线程中执行录音操作，以免阻塞主线程。