Android Audio代码分析3

今天来看看类AudioTrack的构造函数。

出发点是Java中的AudioTrack类。

从前面的使用实例中可知，应用程序中要实现播放，首先要创建一个AudioTrack对象，然后调用其函数来实现播放。

*****************************************源码*************************************************

    public AudioTrack(int streamType, int sampleRateInHz, int channelConfig, int audioFormat,

            int bufferSizeInBytes, int mode, int sessionId)

    throws IllegalArgumentException {

        mState = STATE_UNINITIALIZED;

        // remember which looper is associated with the AudioTrack instanciation

        if ((mInitializationLooper = Looper.myLooper()) == null) {

            mInitializationLooper = Looper.getMainLooper();

        }

        audioParamCheck(streamType, sampleRateInHz, channelConfig, audioFormat, mode);

        audioBuffSizeCheck(bufferSizeInBytes);

        if (sessionId < 0) {

            throw (new IllegalArgumentException("Invalid audio session ID: "+sessionId));

        }

        int[] session = new int[1];

        session[0] = sessionId;

        // native initialization

        int initResult = native_setup(new WeakReference<AudioTrack>(this),

                mStreamType, mSampleRate, mChannels, mAudioFormat,

                mNativeBufferSizeInBytes, mDataLoadMode, session);

        if (initResult != SUCCESS) {

            loge("Error code "+initResult+" when initializing AudioTrack.");

            return; // with mState == STATE_UNINITIALIZED

        }

        mSessionId = session[0];

        if (mDataLoadMode == MODE_STATIC) {

            mState = STATE_NO_STATIC_DATA;

        } else {

            mState = STATE_INITIALIZED;

        }

    } www.2cto.com

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源码路径：

frameworks\base\media\java\android\media\AudioTrack.java

###########################################说明##############################################################

还是先看看自带注释：

    /**

     * Class constructor with audio session. Use this constructor when the AudioTrack must be

     * attached to a particular audio session. The primary use of the audio session ID is to

     * associate audio effects