diff --git a/app/src/main/java/cc/liuyx/note/activity/BaseActivity.java b/app/src/main/java/cc/liuyx/note/activity/BaseActivity.java
index 4ff049c..a211642 100644
--- a/app/src/main/java/cc/liuyx/note/activity/BaseActivity.java
+++ b/app/src/main/java/cc/liuyx/note/activity/BaseActivity.java
@@ -1,5 +1,6 @@
 package cc.liuyx.note.activity;
 
+import android.annotation.SuppressLint;
 import android.app.Activity;
 import android.content.BroadcastReceiver;
 import android.content.Context;
@@ -21,6 +22,7 @@ import com.githang.statusbar.StatusBarCompat;
 
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
+import java.util.Objects;
 
 public abstract class BaseActivity extends AppCompatActivity {
 
@@ -59,7 +61,6 @@ public abstract class BaseActivity extends AppCompatActivity {
     public void setNightMode(){
         if(isNightMode()) this.setTheme(R.style.NightTheme);
         else setTheme(R.style.DayTheme);
-
     }
 
     protected abstract void needRefresh();
@@ -71,8 +72,7 @@ public abstract class BaseActivity extends AppCompatActivity {
     }
 
     public long calStrToSec(String date) throws ParseException {//decode calender date to second
-        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm");
-        long secTime = format.parse(date).getTime();
-        return secTime;
+        @SuppressLint("SimpleDateFormat") SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm");
+        return Objects.requireNonNull(format.parse(date)).getTime();
     }
 }
diff --git a/app/src/main/java/cc/liuyx/note/activity/EditActivity.java b/app/src/main/java/cc/liuyx/note/activity/EditActivity.java
index 60f7cb0..827cb42 100644
--- a/app/src/main/java/cc/liuyx/note/activity/EditActivity.java
+++ b/app/src/main/java/cc/liuyx/note/activity/EditActivity.java
@@ -24,6 +24,7 @@ import java.text.SimpleDateFormat;
 import java.util.Arrays;
 import java.util.Date;
 import java.util.List;
+import java.util.Objects;
 
 import cc.liuyx.note.db.NoteDatabase;
 
@@ -47,7 +48,7 @@ public class EditActivity extends BaseActivity {
 
         Toolbar myToolbar = (Toolbar) findViewById(R.id.my_toolbar);
         setSupportActionBar(myToolbar);
-        getSupportActionBar().setHomeButtonEnabled(true);
+        Objects.requireNonNull(getSupportActionBar()).setHomeButtonEnabled(true);
 
         getSupportActionBar().setDisplayHomeAsUpEnabled(true);
 
diff --git a/app/src/main/java/cc/liuyx/note/activity/MainActivity.java b/app/src/main/java/cc/liuyx/note/activity/MainActivity.java
index 4fc7889..069577e 100644
--- a/app/src/main/java/cc/liuyx/note/activity/MainActivity.java
+++ b/app/src/main/java/cc/liuyx/note/activity/MainActivity.java
@@ -171,40 +171,40 @@ public class MainActivity extends BaseActivity implements OnItemClickListener, O
                 add_tag = customView.findViewById(R.id.add_tag);
 
                 add_tag.setOnClickListener(new OnClickListener() {
-                    @Override
-                    public void onClick(View v) {
-                        if (sharedPreferences.getString("tagListString", "").split("_").length < 8) {
-                            final EditText et = new EditText(context);
-                            new AlertDialog.Builder(MainActivity.this)
-                                    .setMessage("输入标签名")
-                                    .setView(et)
-                                    .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
-                                        @Override
-                                        public void onClick(DialogInterface dialog, int which) {
-                                            List<String> tagList = Arrays.asList(sharedPreferences.getString("tagListString", null).split("_")); //获取tags
-
-                                            String name = et.getText().toString();
-                                            if (!tagList.contains(name)) {
-                                                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
-                                                String oldTagListString = sharedPreferences.getString("tagListString", null);
-                                                String newTagListString = oldTagListString + "_" + name;
-                                                SharedPreferences.Editor editor = sharedPreferences.edit();
-                                                editor.putString("tagListString", newTagListString);
-                                                editor.apply();
-                                                refreshTagList();
-                                            } else
-                                                Toast.makeText(context, "Repeated tag!", Toast.LENGTH_SHORT).show();
-                                        }
-                                    }).setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {
-                                        @Override
-                                        public void onClick(DialogInterface dialog, int which) {
-                                            dialog.dismiss();
-                                        }
-                                    }).create().show();
-                        } else {
-                            Toast.makeText(context, "自定义的标签够多了！", Toast.LENGTH_SHORT).show();
-                        }
+                @Override
+                public void onClick(View v) {
+                    if (sharedPreferences.getString("tagListString", "").split("_").length < 8) {
+                        final EditText et = new EditText(context);
+                        new AlertDialog.Builder(MainActivity.this)
+                                .setMessage("输入标签名")
+                                .setView(et)
+                                .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
+                                    @Override
+                                    public void onClick(DialogInterface dialog, int which) {
+                                        List<String> tagList = Arrays.asList(sharedPreferences.getString("tagListString", null).split("_")); //获取tags
+
+                                        String name = et.getText().toString();
+                                        if (!tagList.contains(name)) {
+                                            SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
+                                            String oldTagListString = sharedPreferences.getString("tagListString", null);
+                                            String newTagListString = oldTagListString + "_" + name;
+                                            SharedPreferences.Editor editor = sharedPreferences.edit();
+                                            editor.putString("tagListString", newTagListString);
+                                            editor.apply();
+                                            refreshTagList();
+                                        } else
+                                            Toast.makeText(context, "Repeated tag!", Toast.LENGTH_SHORT).show();
+                                    }
+                                }).setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {
+                                    @Override
+                                    public void onClick(DialogInterface dialog, int which) {
+                                        dialog.dismiss();
+                                    }
+                                }).create().show();
+                    } else {
+                        Toast.makeText(context, "自定义的标签够多了！", Toast.LENGTH_SHORT).show();
                     }
+                }
                 });
 
                 //final SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
@@ -481,8 +481,8 @@ public class MainActivity extends BaseActivity implements OnItemClickListener, O
         else myToolbar.setTitle("所有笔记");
     }
 
+    @SuppressLint("InflateParams")
     public void initPopupView() {
-        //instantiate the popup.xml layout file
         layoutInflater = (LayoutInflater) MainActivity.this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
         customView = (ViewGroup) layoutInflater.inflate(R.layout.setting_layout, null);
         coverView = (ViewGroup) layoutInflater.inflate(R.layout.setting_cover, null);
@@ -496,8 +496,6 @@ public class MainActivity extends BaseActivity implements OnItemClickListener, O
     }
 
     private void initPrefs() {
-        //initialize all useful SharedPreferences for the first time the app runs
-
         sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getBaseContext());
         SharedPreferences.Editor editor = sharedPreferences.edit();
         if (!sharedPreferences.contains("nightMode")) {
diff --git a/app/src/main/java/cc/liuyx/note/alarm/AlarmReceiver.java b/app/src/main/java/cc/liuyx/note/alarm/AlarmReceiver.java
index ef6c740..0c2ae83 100644
--- a/app/src/main/java/cc/liuyx/note/alarm/AlarmReceiver.java
+++ b/app/src/main/java/cc/liuyx/note/alarm/AlarmReceiver.java
@@ -35,15 +35,12 @@ public class AlarmReceiver extends BroadcastReceiver {
             manager.createNotificationChannel(mChannel);
         }
 
-
         NotificationCompat.Builder builder = new NotificationCompat.Builder(context, channelId)
                 .setContentTitle(title).setContentText(content).setSmallIcon(R.drawable.red_alarm_24dp)
                 .setContentIntent(pendingIntent).setAutoCancel(true).setFullScreenIntent(pendingIntent, true);
 
         Notification notification = builder.build();
 
-
         manager.notify(1, notification);
-
     }
 }