Add quick toggle shortcut (#950)

Mainly for Android 7.1, also backward compatible.

src/main/AndroidManifest.xml

@@ -53,6 +53,8 @@
             <intent-filter>
                 <action android:name="android.service.quicksettings.action.QS_TILE" />
             </intent-filter>
+            <meta-data android:name="android.app.shortcuts"
+                       android:resource="@xml/shortcuts"/>
         </activity>
 
         <activity
@@ -116,6 +118,17 @@
             </intent-filter>
         </activity>
 
+        <activity
+                android:name=".QuickToggleShortcut"
+                android:label="@string/quick_toggle"
+                android:theme="@android:style/Theme.NoDisplay"
+                android:excludeFromRecents="true"
+                android:launchMode="singleTask">
+            <intent-filter>
+                <action android:name="android.intent.action.CREATE_SHORTCUT" />
+            </intent-filter>
+        </activity>
+
         <service
                 android:name=".ShadowsocksRunnerService"
                 android:exported="false">

src/main/res/xml/shortcuts.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shortcuts xmlns:android="http://schemas.android.com/apk/res/android">
+    <shortcut android:shortcutId="toggle"
+              android:enabled="true"
+              android:icon="@mipmap/ic_launcher"
+              android:shortcutShortLabel="@string/quick_toggle"
+              android:shortcutLongLabel="@string/quick_toggle"
+              android:shortcutDisabledMessage="@string/quick_toggle">
+        <intent android:action="android.intent.action.VIEW"
+                android:targetPackage="com.github.shadowsocks"
+                android:targetClass="com.github.shadowsocks.QuickToggleShortcut" />
+    </shortcut>
+</shortcuts>

src/main/scala/com/github/shadowsocks/QuickToggleShortcut.scala

@@ -0,0 +1,39 @@
+package com.github.shadowsocks
+
+import android.app.Activity
+import android.content.Intent
+import android.os.Bundle
+import com.github.shadowsocks.utils.{State, Utils}
+
+/**
+  * @author Mygod
+  */
+class QuickToggleShortcut extends Activity with ServiceBoundContext {
+  override def onCreate(savedInstanceState: Bundle) {
+    super.onCreate(savedInstanceState)
+    getIntent.getAction match {
+      case Intent.ACTION_CREATE_SHORTCUT =>
+        setResult(Activity.RESULT_OK, new Intent()
+          .putExtra(Intent.EXTRA_SHORTCUT_INTENT, new Intent(this, classOf[QuickToggleShortcut]))
+          .putExtra(Intent.EXTRA_SHORTCUT_NAME, getString(R.string.quick_toggle))
+          .putExtra(Intent.EXTRA_SHORTCUT_ICON_RESOURCE,
+            Intent.ShortcutIconResource.fromContext(this, R.mipmap.ic_launcher)))
+        finish()
+      case _ => attachService()
+    }
+  }
+
+  override def onDestroy() {
+    detachService()
+    super.onDestroy()
+  }
+
+  override def onServiceConnected() {
+    bgService.getState match {
+      case State.STOPPED => Utils.startSsService(this)
+      case State.CONNECTED => Utils.stopSsService(this)
+      case _ => // ignore
+    }
+    finish()
+  }
+}