修改跟练模式的暂停之后无法restart的问题

musictuner/src/main/java/com/cooleshow/musictuner/utils/MusicTunerHelper.java

@@ -22,9 +22,7 @@ public class MusicTunerHelper {
     }
 
     public void start() {
-        if (mDispatcher == null) {
-            mDispatcher = AudioDispatcherFactory.fromDefaultMicrophone(22050, 2048, 0);
-        }
+        mDispatcher = AudioDispatcherFactory.fromDefaultMicrophone(22050, 2048, 0);
         PitchDetectionHandler pdh = new PitchDetectionHandler() {
             @Override
             public void handlePitch(PitchDetectionResult res, AudioEvent e) {