diff --git a/.travis.yml b/.travis.yml
index d6289e3..2b40e65 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,8 @@
 language: android
 jdk: oraclejdk8
-
+dist: xenial
+git:
+  depth: 1
 android:
   components:
     - tools
@@ -12,8 +14,6 @@ android:
     - extra-android-m2repository
   licenses:
     - '.+'
-before_install:
-- yes | sdkmanager "platforms;android-28"
 script:
   - chmod 777 gradlew
   - ./gradlew clean assembleDebug
diff --git a/README.md b/README.md
index 9cc579c..86e3138 100644
--- a/README.md
+++ b/README.md
@@ -48,8 +48,8 @@ __Users must comply with local laws and regulations.__<br>
 
 * __CuteDNS__ - *Shutdown according to regulations*
 * __[FUN DNS](http://fundns.cn)__ - *Shutdown according to regulations*
-* __[Pure DNS](https://puredns.cn/)__
-* __[PdoMo-DNS](https://pdomo.me/)__ - *Intelligent Free Public DNS*
+* __[Pure DNS](https://puredns.cn/)__ - *Shutdown according to regulations*
+* __[PdoMo-DNS](https://pdomo.me/)__ - *Shutdown according to regulations*
 * __[rubyfish](https://www.rubyfish.cn)__ - *Free DoT/DoH DNS*
 
 ## Rule Providers
@@ -60,9 +60,8 @@ __Users must comply with local laws and regulations.__<br>
 
 ## Requirements
 
-* Minimum Android version: 4.0.3 (API 15) - __*Basic VPN functions*__
-* Recommended Android version: >= 5.0 (API 21) - __*Full features*__
-* Best Android version: >= 7.1 (API 25) - __*Launcher shortcuts*__
+* Minimum Android version: >= 5.0 (API 21)
+* Recommended Android version: >= 7.1 (API 25) - __*Launcher shortcuts*__
 
 ## Open Source Licenses
 
diff --git a/app/src/main/java/org/itxtech/daedalus/Daedalus.java b/app/src/main/java/org/itxtech/daedalus/Daedalus.java
index 9f9130e..83b8969 100644
--- a/app/src/main/java/org/itxtech/daedalus/Daedalus.java
+++ b/app/src/main/java/org/itxtech/daedalus/Daedalus.java
@@ -49,6 +49,9 @@ public class Daedalus extends Application {
         add(new DNSServer("101.101.101.101", R.string.server_twnic_primary));
         add(new DNSServer("101.102.103.104", R.string.server_twnic_secondary));
         add(new DNSServer("dns.rubyfish.cn/dns-query", R.string.server_rubyfish));
+        add(new DNSServer("cloudflare-dns.com/dns-query", R.string.server_cloudflare));
+        add(new DNSServer("dns.google/dns-query", R.string.server_google_ietf));
+        add(new DNSServer("dns.google/resolve", R.string.server_google_json));
     }};
 
     public static final List<Rule> RULES = new ArrayList<Rule>() {{
diff --git a/app/src/main/java/org/itxtech/daedalus/activity/FilterAppProxyActivity.java b/app/src/main/java/org/itxtech/daedalus/activity/FilterAppProxyActivity.java
index 28a487a..7f5b52a 100644
--- a/app/src/main/java/org/itxtech/daedalus/activity/FilterAppProxyActivity.java
+++ b/app/src/main/java/org/itxtech/daedalus/activity/FilterAppProxyActivity.java
@@ -127,7 +127,7 @@ public class FilterAppProxyActivity extends AppCompatActivity {
                 }
             }
 
-            runOnUiThread(() -> notifyDataSetChanged());
+            runOnUiThread(this::notifyDataSetChanged);
         }
 
         @NonNull
diff --git a/app/src/main/java/org/itxtech/daedalus/fragment/GlobalConfigFragment.java b/app/src/main/java/org/itxtech/daedalus/fragment/GlobalConfigFragment.java
index 849c88b..403aa49 100644
--- a/app/src/main/java/org/itxtech/daedalus/fragment/GlobalConfigFragment.java
+++ b/app/src/main/java/org/itxtech/daedalus/fragment/GlobalConfigFragment.java
@@ -1,13 +1,8 @@
 package org.itxtech.daedalus.fragment;
 
 import android.content.Intent;
-import android.os.Build;
 import android.os.Bundle;
 import android.preference.*;
-import android.view.View;
-
-import com.google.android.material.snackbar.Snackbar;
-
 import org.itxtech.daedalus.Daedalus;
 import org.itxtech.daedalus.R;
 import org.itxtech.daedalus.activity.FilterAppProxyActivity;
@@ -78,26 +73,14 @@ public class GlobalConfigFragment extends PreferenceFragment {
             return true;
         });
 
-        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
-            SwitchPreference advanced = (SwitchPreference) findPreference("settings_advanced_switch");
-            advanced.setEnabled(false);
-            advanced.setChecked(false);
-            SwitchPreference boot = (SwitchPreference) findPreference("settings_boot");
-            boot.setEnabled(false);
-            boot.setChecked(false);
-            SwitchPreference app_filter = (SwitchPreference) findPreference("settings_app_filter_switch");
-            app_filter.setEnabled(false);
-            app_filter.setChecked(false);
-        }
-
         SwitchPreference advanced = (SwitchPreference) findPreference("settings_advanced_switch");
         advanced.setOnPreferenceChangeListener((preference, newValue) -> {
             updateOptions((boolean) newValue, "settings_advanced");
             return true;
         });
 
-        SwitchPreference app_filter = (SwitchPreference) findPreference("settings_app_filter_switch");
-        app_filter.setOnPreferenceChangeListener((p, w) -> {
+        SwitchPreference appFilter = (SwitchPreference) findPreference("settings_app_filter_switch");
+        appFilter.setOnPreferenceChangeListener((p, w) -> {
             updateOptions((boolean) w, "settings_app_filter");
             return true;
         });
@@ -128,7 +111,7 @@ public class GlobalConfigFragment extends PreferenceFragment {
         });
 
         updateOptions(advanced.isChecked(), "settings_advanced");
-        updateOptions(app_filter.isChecked(), "settings_app_filter");
+        updateOptions(appFilter.isChecked(), "settings_app_filter");
     }
 
     private void updateOptions(boolean checked, String pref) {
@@ -145,13 +128,4 @@ public class GlobalConfigFragment extends PreferenceFragment {
             }
         }
     }
-
-    @Override
-    public void onViewCreated(View view, Bundle savedInstanceState) {
-        super.onViewCreated(view, savedInstanceState);
-
-        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
-            Snackbar.make(view, R.string.notice_legacy_api, Snackbar.LENGTH_LONG).show();
-        }
-    }
 }
diff --git a/app/src/main/res/values-zh-rCN/strings.xml b/app/src/main/res/values-zh-rCN/strings.xml
index 05ee9a3..9ff148d 100644
--- a/app/src/main/res/values-zh-rCN/strings.xml
+++ b/app/src/main/res/values-zh-rCN/strings.xml
@@ -7,7 +7,6 @@
     <string name="notice_activated">已启用 iTXTech Daedalus。</string>
     <string name="notice_start_test">正在测试指定的 DNS 服务器……</string>
     <string name="notice_queries">DNS 查询次数:</string>
-    <string name="notice_legacy_api">当前 Android API 无法支持所有功能。</string>
     <string name="notice_need_restart">重新启用 Daedalus 以应用设置。</string>
     <string name="notice_start_download">正在下载规则，请稍等 ……</string>
     <string name="notice_downloaded">已下载规则。</string>
@@ -86,11 +85,12 @@
     <string name="settings_app_filter_list">选择应用</string>
     <string name="settings_app_filter_mode">黑名单模式</string>
     <string name="settings_app_filter_list_summary">选择要过滤的应用</string>
-    <string name="settings_app_filter_summary">仅支持Android Lollipop及以上版本</string>
 
     <string name="server_twnic_primary">Quad 101 主服务器</string>
     <string name="server_twnic_secondary">Quad 101 辅服务器</string>
     <string name="server_rubyfish">红鱼 (DoH)</string>
+    <string name="server_google_json">谷歌公共 DNS (DoH JSON)</string>
+    <string name="server_google_ietf">谷歌公共 DNS (DoH RFC8484)</string>
 
     <string name="primary_server">首选 DNS 服务器</string>
     <string name="secondary_server">备用 DNS 服务器</string>
diff --git a/app/src/main/res/values-zh-rTW/strings.xml b/app/src/main/res/values-zh-rTW/strings.xml
index 5aae473..9aa95ab 100644
--- a/app/src/main/res/values-zh-rTW/strings.xml
+++ b/app/src/main/res/values-zh-rTW/strings.xml
@@ -7,7 +7,6 @@
     <string name="notice_activated">已啟動 iTXTech Daedalus。</string>
     <string name="notice_start_test">正在測試指定的 DNS 伺服器……</string>
     <string name="notice_queries">DNS 查詢次數:</string>
-    <string name="notice_legacy_api">目前 Android API 無法支援所有功能。</string>
     <string name="notice_need_restart">重新啟動 Daedalus 以套用設定。</string>
     <string name="notice_start_download">正在下載規則，請稍等……</string>
     <string name="notice_downloaded">已下載規則。</string>
@@ -64,7 +63,7 @@
     <string name="settings_manual_summary">造訪 GitHub wiki 頁面。</string>
     <string name="settings_log_size">紀錄檔大小限制</string>
     <string name="settings_debug_output">调试输出 TODO</string>
-    <string name="settings_dont_build_doh_cache">不缓存 DoH DNS 的 IP地址</string>
+    <string name="settings_dont_build_doh_cache">不緩存 DoH DNS 的 IP地址</string>
     <string name="settings_dark_theme">使用暗主题</string>
 
     <string name="settings_rule_name">規則名稱</string>
@@ -86,7 +85,6 @@
     <string name="settings_app_filter_list">選擇應用</string>
     <string name="settings_app_filter_mode">黑名單模式</string>
     <string name="settings_app_filter_list_summary">選擇要過濾的應用</string>
-    <string name="settings_app_filter_summary">僅支持Android Lollipop及以上版本</string>
 
     <string name="server_twnic_primary">Quad 101 主伺服器</string>
     <string name="server_twnic_secondary">Quad 101 輔伺服器</string>
diff --git a/app/src/main/res/values/strings.xml b/app/src/main/res/values/strings.xml
index d0cf25c..62e2d9b 100644
--- a/app/src/main/res/values/strings.xml
+++ b/app/src/main/res/values/strings.xml
@@ -6,7 +6,6 @@
     <string name="notice_activated">iTXTech Daedalus is activated.</string>
     <string name="notice_start_test">Testing specified DNS server…</string>
     <string name="notice_queries">DNS query times:</string>
-    <string name="notice_legacy_api">The current Android API can not support all the features.</string>
     <string name="notice_need_restart">Re-activate Daedalus to make the settings take effect.</string>
     <string name="notice_start_download">Downloading rule, please wait …</string>
     <string name="notice_downloaded">Rule has been downloaded.</string>
@@ -91,11 +90,13 @@
     <string name="settings_app_filter_mode">Blacklist mode</string>
     <string name="settings_app_filter_list">Select application</string>
     <string name="settings_app_filter_list_summary">Select apps to pass through</string>
-    <string name="settings_app_filter_summary">Only supports Android Lollipop and above</string>
 
     <string name="server_twnic_primary">Quad 101 Primary</string>
     <string name="server_twnic_secondary">Quad 101 Secondary</string>
     <string name="server_rubyfish">rubyfish (DoH)</string>
+    <string name="server_cloudflare">Cloudflare DNS (DoH)</string>
+    <string name="server_google_json">Google Public DNS (DoH JSON)</string>
+    <string name="server_google_ietf">Google Public DNS (DoH RFC8484)</string>
 
     <string name="primary_server">Primary DNS server</string>
     <string name="secondary_server">Secondary DNS server</string>
diff --git a/app/src/main/res/xml/perf_settings.xml b/app/src/main/res/xml/perf_settings.xml
index 0a5f9cd..5540e8c 100644
--- a/app/src/main/res/xml/perf_settings.xml
+++ b/app/src/main/res/xml/perf_settings.xml
@@ -54,7 +54,6 @@
         <SwitchPreference
             android:key="settings_app_filter_switch"
             android:title="@string/settings_app_filter"
-            android:summary="@string/settings_app_filter_summary"
             android:defaultValue="false"/>
         <SwitchPreference
             android:key="settings_app_filter_mode_switch"
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 68c1981..d5d6d51 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https://services.gradle.org/distributions/gradle-4.6-bin.zip
+distributionUrl=https://services.gradle.org/distributions/gradle-5.5.1-bin.zip