diff --git a/app/src/main/java/me/bello/mathscalc/activity/CalcActivity.java b/app/src/main/java/me/bello/mathscalc/activity/CalcActivity.java
index f4ed8bf..fa56348 100755
--- a/app/src/main/java/me/bello/mathscalc/activity/CalcActivity.java
+++ b/app/src/main/java/me/bello/mathscalc/activity/CalcActivity.java
@@ -125,7 +125,7 @@
             @Override
             public void onTick(long l) {
                 // 显示倒计时值
-                AnimUtils.animAlpha(timerText);
+//                AnimUtils.animAlpha(timerText);
                 timerText.setText((l / 1000) + "");
             }
 
@@ -489,13 +489,20 @@
         new Handler().postDelayed(new Runnable() {
             @Override
             public void run() {
-                mediaPlayer.stop();
-                mediaPlayer.release();
-                mediaPlayer = null;
+                if (null != mediaPlayer) {
+                    mediaPlayer.stop();
+                    mediaPlayer.release();
+                    mediaPlayer = null;
+                }
             }
         }, 1000);
     }
 
+    @Override
+    protected void onDestroy() {
+        timer.cancel();
+        super.onDestroy();
+    }
 
     @Override
     public boolean onKeyDown(int keyCode, KeyEvent event) {