跟踪手指在屏幕上的位置生成音频样本并播放
此示例根据用户手指在屏幕的x轴方向上的位置，来选择频率并生成音频样本。
因为代码比较简单，那么话不多说，直接上代码。
public class FingerSynthesis extends Activity implements OnTouchListener{AudioSynthesisTask audioSynth;//播放音频样本的线程static final float BASE_FREQUENCY = 440;//基准音频频率float synth_frequency = BASE_FREQUENCY; // 440 Hz, 随着手指的移动会发生改变boolean play = false;//控制是否生成音频样本@Overridepublic void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.main);View mainView = this.findViewById(R.id.MainView);mainView.setOnTouchListener(this);audioSynth = new AudioSynthesisTask();audioSynth.execute();}@Overridepublic void onPause(){super.onPause();play = false;finish();}public boolean onTouch(View v, MotionEvent event){int action = event.getAction();switch (action){case MotionEvent.ACTION_DOWN:play = true;//根据用户操作将play设置为true或者falsesynth_frequency = event.getX() + BASE_FREQUENCY;//跟踪用户手指的位置，做出相应的改变Log.v("FREQUENCY", "" + synth_frequency);break;case MotionEvent.ACTION_MOVE:play = true;synth_frequency = event.getX() + BASE_FREQUENCY;Log.v("FREQUENCY", "" + synth_frequency);break;case MotionEvent.ACTION_UP:play = false;break;case MotionEvent.ACTION_CANCEL:break;default:break;}return true;}private class AudioSynthesisTask extends AsyncTask<Void, Void, Void>{@Overrideprotected Void doInBackground(Void... params){final int SAMPLE_RATE = 11025;int minSize = AudioTrack.getMinBufferSize(SAMPLE_RATE,AudioFormat.CHANNEL_CONFIGURATION_MONO,AudioFormat.ENCODING_PCM_16BIT);AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,SAMPLE_RATE, AudioFormat.CHANNEL_CONFIGURATION_MONO,AudioFormat.ENCODING_PCM_16BIT, minSize,AudioTrack.MODE_STREAM);audioTrack.play();short[] buffer = new short[minSize];float angle = 0;while (true){if (play){for (int i = 0; i < buffer.length; i++){float angular_frequency = (float) (2 * Math.PI)* synth_frequency / SAMPLE_RATE;buffer[i] = (short) (Short.MAX_VALUE * ((float) Math.sin(angle)));//生成音频样本angle += angular_frequency;}audioTrack.write(buffer, 0, buffer.length);} else{try{Thread.sleep(50);} catch (InterruptedException e){e.printStackTrace();}}}}}}