1、优化toast居中展示；

lib/utils/toast_util.dart

@@ -14,8 +14,7 @@ class ToastUtil {
         toastLength: toastDuration == ToastDuration.long
             ? Toast.LENGTH_LONG
             : Toast.LENGTH_SHORT,
-        // ios 软键盘遮挡toast，设置中心展示
-        gravity: Platform.isIOS ? ToastGravity.CENTER : ToastGravity.BOTTOM,
+        gravity: ToastGravity.CENTER,
         // timeInSecForIos: 1,
         backgroundColor: const Color(0xB3000000),
         textColor: Colors.white,