Add help for kcpcli (#811)

* Add help for kcpcli

* Filter useless parameters

src/main/res/xml/pref_all.xml

@@ -94,7 +94,7 @@
                 android:summary="@string/kcp_port_summary"
                 android:title="@string/kcp_port"/>
 
-        <com.github.shadowsocks.preferences.SummaryEditTextPreference
+        <com.github.shadowsocks.preferences.KcpCliPreference
                 android:key="kcpcli"
                 android:persistent="false"
                 android:summary="@string/kcpcli_summary"

src/main/scala/com/github/shadowsocks/preferences/KcpCliPreference.scala

@@ -0,0 +1,38 @@
+package com.github.shadowsocks.preferences
+
+import android.app.AlertDialog
+import android.content.{Context, DialogInterface}
+import android.util.AttributeSet
+import android.view.ViewGroup
+import eu.chainfire.libsuperuser.Shell
+
+import scala.collection.JavaConversions._
+
+/**
+  * @author Mygod
+  */
+class KcpCliPreference(context: Context, attrs: AttributeSet) extends SummaryEditTextPreference(context, attrs) {
+  override def onPrepareDialogBuilder(builder: AlertDialog.Builder) {
+    super.onPrepareDialogBuilder(builder)
+    builder.setNeutralButton("?", ((_, _) => {
+      val dialog = new AlertDialog.Builder(context)
+        .setTitle("?")
+        .setMessage(asScalaBuffer(Shell.SH.run(context.getApplicationInfo.dataDir + "/kcptun --help"))
+          .dropWhile(line => line != "GLOBAL OPTIONS:")
+          .drop(1)
+          .takeWhile(line => line.length() > 3)
+          .filter(line =>
+            !line.startsWith("   --localaddr ") &&
+            !line.startsWith("   --remoteaddr ") &&
+            !line.startsWith("   --path ") &&
+            !line.startsWith("   --help,") &&
+            !line.startsWith("   --version,"))
+          .mkString("\n"))
+        .show()
+      val window = dialog.getWindow
+      val attrs = window.getAttributes
+      attrs.width = ViewGroup.LayoutParams.MATCH_PARENT
+      window.setAttributes(attrs)
+    }): DialogInterface.OnClickListener)
+  }
+}