跟踪手指在屏幕上的位置生成音频样本并播放 (一)

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。

[java]
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

@Override
public 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();
}

@Override
public 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false
synth_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;