android ffmpeg+opensl 音频解码播放、暂停、进度seek、时间、上/下一首

类似文章太多，但是大多代码都有内存溢出的问题，而且都缺少c层调用java层的例子，实际上有了参考博文后，还是有很多坑需要自己填。不过，看了很多博主和帖子后还是能够解决一些问题，但是有些问题，根本找不到，所以我把音频解码播放还有控制部分做了比较详细的例子。

ffmpeg的编译请参考我之前的文章，有编好的库文件在我的下载资源里，github的demo里也有。

opensl库的引用也很简单，cmak里加入opensl就可以了，像这样

target_link_libraries( native-lib
                       android
                       ffmpeg
                       OpenSLES
                       ${log-lib} )

opensl使用步骤大概分三步

• 创建OpenSLES引擎

 //创建OpenSLES引擎
extern "C"
void createEngine() {
    SLresult result;
    //创建引擎
    result = slCreateEngine(&engineObject, 0, NULL, 0, NULL, NULL);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    //关联引擎
    result = (*engineObject)->Realize(engineObject, SL_BOOLEAN_FALSE);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    //获取引擎接口, which is needed in order to create other objects
    result = (*engineObject)->GetInterface(engineObject, SL_IID_ENGINE, &engineEngine);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    //创建输出混音器, with environmental reverb specified as a non-required interface
    const SLInterfaceID ids[1] = {SL_IID_ENVIRONMENTALREVERB};
    const SLboolean req[1] = {SL_BOOLEAN_FALSE};
    result = (*engineEngine)->CreateOutputMix(engineEngine, &outputMixObject, 1, ids, req);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    //关联输出混音器
    result = (*outputMixObject)->Realize(outputMixObject, SL_BOOLEAN_FALSE);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    // get the environmental reverb interface
    // this could fail if the environmental reverb effect is not available,
    // either because the feature is not present, excessive CPU load, or
    // the required MODIFY_AUDIO_SETTINGS permission was not requested and granted
    //获取reverb接口
    result = (*outputMixObject)->GetInterface(outputMixObject, SL_IID_ENVIRONMENTALREVERB,
                                              &outputMixEnvironmentalReverb);
    if (SL_RESULT_SUCCESS == result) {
        result = (*outputMixEnvironmentalReverb)->SetEnvironmentalReverbProperties(
                outputMixEnvironmentalReverb, &reverbSettings);
        (void) result;
    }
    // ignore unsuccessful result codes for environmental reverb, as it is optional for this example
}

• 创建缓存队列和opensl播放器

// create buffer queue audio player
extern "C"
void createBufferQueueAudioPlayer(int sampleRate, int channel) {
    SLresult result;
    if (sampleRate >= 0) {
        bqPlayerSampleRate = sampleRate * 1000;

    }
    //配置音频源
    SLDataLocator_AndroidSimpleBufferQueue loc_bufq = {SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE, 2};
    SLDataFormat_PCM format_pcm = {SL_DATAFORMAT_PCM, 1, SL_SAMPLINGRATE_8,
                                   SL_PCMSAMPLEFORMAT_FIXED_16, SL_PCMSAMPLEFORMAT_FIXED_16,
                                   SL_SPEAKER_FRONT_CENTER, SL_BYTEORDER_LITTLEENDIAN};
    if (bqPlayerSampleRate) {
        format_pcm.samplesPerSec = bqPlayerSampleRate;       //sample rate in mili second
    }
    format_pcm.numChannels = (SLuint32) channel;
    if (channel == 2) {
        format_pcm.channelMask = SL_SPEAKER_FRONT_LEFT | SL_SPEAKER_FRONT_RIGHT;
    } else {
        format_pcm.channelMask = SL_SPEAKER_FRONT_CENTER;
    }
    SLDataSource audioSrc = {&loc_bufq, &format_pcm};

    //配置音频池
    SLDataLocator_OutputMix loc_outmix = {SL_DATALOCATOR_OUTPUTMIX, outputMixObject};
    SLDataSink audioSnk = {&loc_outmix, NULL};
    /*
     * create audio player:
     *     fast audio does not support when SL_IID_EFFECTSEND is required, skip it
     *     for fast audio case
     */
    const SLInterfaceID ids[3] = {SL_IID_BUFFERQUEUE, SL_IID_VOLUME, SL_IID_EFFECTSEND,
            /*SL_IID_MUTESOLO,*/};
    const SLboolean req[3] = {SL_BOOLEAN_TRUE, SL_BOOLEAN_TRUE, SL_BOOLEAN_TRUE,
            /*SL_BOOLEAN_TRUE,*/ };
    //创建音频播放器
    result = (*engineEngine)->CreateAudioPlayer(engineEngine, &bqPlayerObject, &audioSrc, &audioSnk,
                                                bqPlayerSampleRate ? 2 : 3, ids, req);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    // 关联播放器
    result = (*bqPlayerObject)->Realize(bqPlayerObject, SL_BOOLEAN_FALSE);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    // 获取播放接口
    result = (*bqPlayerObject)->GetInterface(bqPlayerObject, SL_IID_PLAY, &bqPlayerPlay);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    // 获取缓冲队列接口
    result = (*bqPlayerObject)->GetInterface(bqPlayerObject, SL_IID_BUFFERQUEUE,
                                             &bqPlayerBufferQueue);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    // 注册缓冲队列回调
    result = (*bqPlayerBufferQueue)->RegisterCallback(bqPlayerBufferQueue, bqPlayerCallback, NULL);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    // 获取音效接口
    bqPlayerEffectSend = NULL;
    if (0 == bqPlayerSampleRate) {
        result = (*bqPlayerObject)->GetInterface(bqPlayerObject, SL_IID_EFFECTSEND,
                                                 &bqPlayerEffectSend);
        assert(SL_RESULT_SUCCESS == result);
        (void) result;
    }
#if 0   // mute/solo is not supported for sources that are known to be mono, as this is
    // get the mute/solo interface
    result = (*bqPlayerObject)->GetInterface(bqPlayerObject, SL_IID_MUTESOLO, &bqPlayerMuteSolo);
    assert(SL_RESULT_SUCCESS == result);
    (void)result;
#endif
    // 获取音量接口
    result = (*bqPlayerObject)->GetInterface(bqPlayerObject, SL_IID_VOLUME, &bqPlayerVolume);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    //注册事件回调
    result = (*bqPlayerPlay)->RegisterCallback(bqPlayerPlay, playOverEvent, NULL);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    //设置播放结束回调
    result = (*bqPlayerPlay)->SetCallbackEventsMask(bqPlayerPlay, SL_PLAYEVENT_HEADATEND);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
    // 开始播放音乐
    result = (*bqPlayerPlay)->SetPlayState(bqPlayerPlay, SL_PLAYSTATE_PAUSED);
    assert(SL_RESULT_SUCCESS == result);
    (void) result;
}

• 实现数据回调方法

void releaseResampleBuf(void) {
    if (0 == bqPlayerSampleRate) {
        /*
         * we are not using fast path, so we were not creating buffers, nothing to do
         */
        return;
    }
    free(resampleBuf);
    resampleBuf = NULL;
}

// this callback handler is called every time a buffer finishes playing
extern "C"
void bqPlayerCallback(SLAndroidSimpleBufferQueueItf bq, void *context) {
    assert(bq == bqPlayerBufferQueue);
    assert(NULL == context);
    // for streaming playback, replace this test by logic to find and fill the next buffer
    if (getPCM() < 0) {//解码音频文件
        pthread_mutex_unlock(&audioEngineLock);
        return;
    }
    if (NULL != nextBuffer && 0 != nextSize) {
        SLresult result;
        // enqueue another buffer
        result = (*bqPlayerBufferQueue)->Enqueue(bqPlayerBufferQueue, nextBuffer, nextSize);
        // the most likely other result is SL_RESULT_BUFFER_INSUFFICIENT,
        // which for this code example would indicate a programming error
        if (SL_RESULT_SUCCESS != result) {
            pthread_mutex_unlock(&audioEngineLock);
        }
        (void) result;
    } else {
        releaseResampleBuf();
        pthread_mutex_unlock(&audioEngineLock);
    }
}

基本就这三步，在我理解里，其实opensl就是一个播放器的api，我们这里也就是简单调用封装好的方法而已。

播放音频当然还需要数据，opensl本身可以读assert、uri的音频数据、pcm数据，我这里因为是为了后面音视频做铺垫，所以加入了ffmpeg来解码音频数据得到pcm数据后，扔到opensl缓存队列就可以了。

具体的解码过程如下：

extern "C"
//int createFFmpegAudioPlay(const char *file_name) {
int Java_com_lake_ndkaudiotest_MainActivity_play(JNIEnv *env, jobject thiz, jstring url) {
    isEnd = false;
    int i;
    AVCodec *pCodec;
    //读取输入的音频文件地址
    const char *file_name = env->GetStringUTFChars(url, NULL);
    LOGI("file_name:%s\n", file_name);
    //初始化
    av_register_all();
    //分配一个AVFormatContext结构
    pFormatCtx = avformat_alloc_context();
    //打开文件
    if (avformat_open_input(&pFormatCtx, file_name, NULL, NULL) != 0) {
        LOGE("Couldn't open input stream.\n");
        return -1;
    }
    //查找文件的流信息
    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
        LOGE("Couldn't find stream information.\n");
        return -1;
    }
    //在流信息中找到音频流
    audioindex = -1;
    for (i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
            audioindex = i;
            break;
        }
    }
    if (audioindex == -1) {
        LOGE("Couldn't find a video stream.\n");
        return -1;
    }
    iTotalSeconds = (int) pFormatCtx->duration / 1000000;
    //获取相应音频流的解码器
    AVCodecParameters *pCodecPar = pFormatCtx->streams[audioindex]->codecpar;
    pCodec = avcodec_find_decoder(pCodecPar->codec_id);
    assert(pCodec != NULL);
    pCodecCtx = avcodec_alloc_context3(pCodec);
    // Copy context
    if (avcodec_parameters_to_context(pCodecCtx, pCodecPar) != 0) {
        fprintf(stderr, "Couldn't copy codec context");
        return -1; // Error copying codec context
    }
    //打开解码器
    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        LOGE("Couldn't open codec.\n");
        return -1;
    }
    //分配一个帧指针，指向解码后的原始帧
    pFrame = av_frame_alloc();
    //设置格式转换
    swr = swr_alloc();
    swr = swr_alloc_set_opts(NULL,
                             pCodecCtx->channel_layout,
                             AV_SAMPLE_FMT_S16,
                             pCodecCtx->sample_rate,
                             pCodecCtx->channel_layout,
                             pCodecCtx->sample_fmt,
                             pCodecCtx->sample_rate,
                             0, NULL);
    if (!swr || swr_init(swr) < 0) {
        swr_free(&swr);
        return -1;
    }
    swr_init(swr);
    //分配输入缓存
    int outputBufferSize = 8192;
    outputBuffer = (uint8_t *) malloc(sizeof(uint8_t) * outputBufferSize);
    // 创建播放引擎
    createEngine();
    // 创建缓冲队列音频播放器
    createBufferQueueAudioPlayer(pCodecCtx->sample_rate, pCodecCtx->channels);
    // 启动音频播放
    bqPlayerCallback(bqPlayerBufferQueue, NULL);
    return 0;
}

opensl获取pcm数据方法

/**
 * 读取pcm数据
 * @return
 */
int getPCM() {
    while (av_read_frame(pFormatCtx, &packet) >= 0) {
        if (packet.stream_index == audioindex) {
            int ret = avcodec_send_packet(pCodecCtx, &packet);
            timestamp = packet.pts * av_q2d(pFormatCtx->streams[audioindex]->time_base);
            if (ret < 0 && ret != AVERROR(EAGAIN) && ret != AVERROR_EOF)
                break;
            ret = avcodec_receive_frame(pCodecCtx, pFrame);
            if (ret < 0 && ret != AVERROR_EOF)
                break;
            //处理不同的格式
            if (pCodecCtx->sample_fmt == AV_SAMPLE_FMT_S16P) {
                nextSize = av_samples_get_buffer_size(pFrame->linesize, pCodecCtx->channels,
                                                      pCodecCtx->frame_size, pCodecCtx->sample_fmt,
                                                      1);
            } else {
                av_samples_get_buffer_size(&nextSize, pCodecCtx->channels, pCodecCtx->frame_size,
                                           pCodecCtx->sample_fmt, 1);
            }
            // 音频格式转换
            swr_convert(swr, &outputBuffer, pFrame->nb_samples,
                        (uint8_t const **) (pFrame->extended_data),
                        pFrame->nb_samples);
            nextBuffer = outputBuffer;
            av_packet_unref(&packet);
            return 0;
        }
        av_packet_unref(&packet);//packet不用了一定要释放掉内存，网上很多例子的内存溢出就是因为没有释放packet的内存。
    }
    LOGI("getPCM_shutdown");
    return -1;
}

有了以上方法，例子参考，基本播放音频是没有问题了。其余的问题都是看个人需求了，我这里就把我的做法分享一下，由于本人c不是太好，虽然实现了，但是从架构上不清楚是不是这样做合不合理，仅供大家参考。

我先说一下我的需求，c层音频播放出来了，但是在java层，我想显示时间，还有控制音频的播放/暂停，以及seek拖动控制，播放完成自动跳下一首。

一开始，我试了一下opensl本身seek功能，结果获取seek接口就失败了，不得不从ffmpeg解码层考虑seek功能，还好，找到了ffmpeg的seek功能，实现起来完全没有问题，后面的视频seek可以参考一下。
其实就是调用以下方法

//跳转的位置（秒为单位）
int64_t seek_pos = (int64_t) (seekTime /av_q2d(pFormatCtx->streams[audioindex]->time_base));
//跳转方法 音频跳转非常快，没有延迟感
if (av_seek_frame(pFormatCtx, audioindex, seek_pos, AVSEEK_FLAG_BACKWARD) < 0) {
   LOGE("%s,  av_seek_frame() seek to %.3f failed!", __FUNCTION__,(double) seek_pos / AV_TIME_BASE);
   return -2;
}
//清空buffer
avcodec_flush_buffers(pCodecCtx);

时间位置获取也非常简单，根据packet获取就可以了

timestamp = packet.pts * av_q2d(pFormatCtx->streams[audioindex]->time_base);

然后java层来调用以下c层实现的seek方法就可以了

然后下来就时间的回调，之前想直接在回调函数里去调java层的方法，但是回调触发到第二遍的时候，就报错了，不知道是不是JNIEnv使用的关系，但是搞了半天就是不可以，没办法，只能自己起一个方法，用一个while循环去监听我所需要回调的数据，然后在这个while里去调java的方法就不会崩溃，所以想直接在opensl的回调方法去调用java层方法感觉有点不科学，不知道能不能实现。

extern "C"
void Java_com_lake_ndkaudiotest_MainActivity_showtime(JNIEnv *env, jobject thiz) {
    int seconds = -1;
    int totalSeconds = -1;
    bool end = false;
    jclass jclazz = env->GetObjectClass(thiz);
    jmethodID jmethodIDS = env->GetMethodID(jclazz, "showTime", "(I)V");
    jmethodID jmethodIDT = env->GetMethodID(jclazz, "setToatalTime", "(I)V");
    jmethodID jmethodIDE = env->GetMethodID(jclazz, "isPlayEnd", "(Z)V");
    // make sure the asset audio player was created
    // seek
    while (true) {
        if (timestamp != -1) {//告诉java 音频播放当前时间
            if (seconds != timestamp) {
                seconds = timestamp;
                env->CallVoidMethod(thiz, jmethodIDS, (jint) timestamp);
            }
        }
        if (iTotalSeconds != -1) {//告诉java 音频总时间
            if (totalSeconds != iTotalSeconds) {
                totalSeconds = iTotalSeconds;
                env->CallVoidMethod(thiz, jmethodIDT, (jint) iTotalSeconds);
            }
        }
        if (isEnd != end) {//告诉java层 音频播放完成
            end = isEnd;
            env->CallVoidMethod(thiz, jmethodIDE, (jboolean) isEnd);
        }
        usleep(100000);//睡0.1秒 不然一直死循环非常占用cpu资源
    }
}

这里利用了监听全局变量，只要一变化就调用java层方法。
java层根据传过来的参数再进行其他处理。

java层代码：

package com.lake.ndkaudiotest;

import android.content.Context;
import android.graphics.Color;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.SeekBar;
import android.widget.TextView;

import java.io.File;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private SeekBar mSeekBar;
    private Thread timeThread;
    private int mProgress;//播放进度
    private ListView listview;
    private TextView tVTime;//当前时间
    private TextView tVName;//名称
    private TextView tTTime;//总时间
    private int toTalTime;//总时间
    private Button mBtnPlayOrPause;
    private Button mBtnLast;
    private Button mBtnNext;
    private String inputurl;//文件路径
    boolean isFirst = true;
    private int curItem = 0;//当前序号
    boolean playing = false;//播放状态
    private int length = 0;//列表长度

    // Used to load the 'native-lib' library on application startup.
    static {
        System.loadLibrary("native-lib");
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        mSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                Log.e("lake", "onProgressChanged: " + progress);
                mProgress = progress;
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                pause(true);
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                seek(mProgress);
            }
        });

    }

    /**
     * 界面初始化
     */
    private void initView() {
        listview = findViewById(R.id.listview);
        tVName = findViewById(R.id.filename);
        tVTime = findViewById(R.id.showtime);
        tTTime = findViewById(R.id.totaltime);
        mSeekBar = findViewById(R.id.seekbar);

        mBtnPlayOrPause = findViewById(R.id.playorpause);
        mBtnLast = findViewById(R.id.last);
        mBtnNext = findViewById(R.id.next);
        mBtnPlayOrPause.setOnClickListener(this);
        mBtnLast.setOnClickListener(this);
        mBtnNext.setOnClickListener(this);


        final String folderurl = Environment.getExternalStorageDirectory().getPath();
        final File[] files = new File(folderurl + "/MyLocalPlayer").listFiles();
        length = files.length;
        final ListFileAdapter myListAdapter = new ListFileAdapter(this, files);
        listview.setAdapter(myListAdapter);
        listview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView parent, View view, int position, long id) {
                curItem = position;
                myListAdapter.setSelectItem(position);
                myListAdapter.notifyDataSetInvalidated();
                inputurl = folderurl + "/MyLocalPlayer/" + files[position].getName();
                tVName.setText(files[position].getName().substring(0,files[position].getName().length()-4));
                if (!isFirst) {
                    stop();
                    mSeekBar.setProgress(0);
                }
                play(inputurl);
                if (isFirst) {
                    isFirst = false;
                    timeThread = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            showtime();
                        }
                    });
                    timeThread.start();
                }
                pause(!playing);
            }
        });
        clickListItem(curItem);

    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.playorpause://播放或者暂停
                pause(playing);
                mBtnPlayOrPause.setText(playing ? "Play" : "Pause");
                playing = !playing;
                break;
            case R.id.last: {//上一首
                int item = (curItem - 1) < 0 ? length-1 : curItem - 1;
                clickListItem(item);
                break;
            }
            case R.id.next: {//下一首
                int item = (curItem + 1) >= length ? 0 : curItem + 1;
                clickListItem(item);
                break;
            }
            default:
                break;
        }
    }

    /**
     * 点击列表
     * @param position 第几项
     */
    public void clickListItem(int position){
        AdapterView.OnItemClickListener onItemClickListener = listview.getOnItemClickListener();
        if (onItemClickListener != null) {
            onItemClickListener.onItemClick(listview, null, position, position);
            listview.setSelection(position);
        }
    }

    /**
     * 关闭播放器
     */
    public void shutdown() {
        stop();
        mSeekBar.setProgress(0);
        play(inputurl);
    }

    /**
     * 显示实时进度时间
     *
     * @param time
     */
    public void showTime(final int time) {
        final String n = resetTimeInt(time / 3600) + ":" + resetTimeInt(time % 3600 / 60) + ":" + resetTimeInt(time % 60);
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                tVTime.setText(n);
                mSeekBar.setProgress(time);
            }
        });
        Log.e("lake", "showTime: " + n);
    }

    /**
     * 设置总时间
     *
     * @param total
     */
    public void setToatalTime(int total) {
        toTalTime = total;
        mSeekBar.setMax(total);
        Log.e("lake", "toTalTime: " + toTalTime);
        final String t = resetTimeInt(total / 3600) + ":" + resetTimeInt(total % 3600 / 60) + ":" + resetTimeInt(total % 60);
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                tTTime.setText(t);
            }
        });
    }

    /**
     * 播放结束
     *
     * @param isEnd
     */
    public void isPlayEnd(boolean isEnd) {
        Log.e("lake", "isPlayEnd: " + isEnd);
        if (isEnd) {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    int item = (curItem + 1) >= length ? 0 : curItem + 1;
                    clickListItem(item);
                }
            });
        }
    }

    public native void play(String url);

    public native void stop();

    public native void pause(boolean play);

    public native void seek(int seekTime);

    public native void showtime();

    public String resetTimeInt(int time) {
        if (time < 10) {
            return "0" + time;
        } else {
            return time + "";
        }
    }

    class ListFileAdapter extends BaseAdapter {
        private Context context;
        private File[] files;

        public ListFileAdapter(Context context, File[] files) {
            this.context = context;
            this.files = files;
        }
        @Override
        public int getCount() {
            return files.length;
        }

        @Override
        public Object getItem(int position) {
            return files[position];
        }

        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder viewHolder = null;
            if (convertView == null) {
                viewHolder = new ViewHolder();
                convertView = LayoutInflater.from(context).inflate(R.layout.list_item, null);
                viewHolder.mTextView = (TextView) convertView.findViewById(R.id.filename);
                convertView.setTag(viewHolder);
            } else {
                viewHolder = (ViewHolder) convertView.getTag();
            }
            viewHolder.mTextView.setText(files[position].getName());
            if (position == selectItem) {
                convertView.setBackgroundColor(Color.GRAY);
            } else {
                convertView.setBackgroundColor(Color.WHITE);
            }
            return convertView;
        }

        class ViewHolder {
            TextView mTextView;
        }

        public void setSelectItem(int selectItem) {
            this.selectItem = selectItem;
        }

        private int selectItem = -1;
    }
}

大概就是这样。
实现的demo下载地址：https://github.com/lakehubo/NDKAudioTest