Preload browser and page to speed up Custom Tabs

app/src/main/AndroidManifest.xml

@@ -5,6 +5,12 @@
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 
+    <queries>
+        <intent>
+            <action android:name="android.support.customtabs.action.CustomTabsService" />
+        </intent>
+    </queries>
+
     <application
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"

app/src/main/java/net/underdesk/circolapp/MainActivity.kt

@@ -19,6 +19,7 @@
 package net.underdesk.circolapp
 
 import android.app.DownloadManager
+import android.content.ComponentName
 import android.content.Context
 import android.content.Intent
 import android.content.pm.PackageManager
@@ -30,6 +31,9 @@ import android.view.MenuItem
 import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.app.AppCompatDelegate
 import androidx.appcompat.widget.SearchView
+import androidx.browser.customtabs.CustomTabsClient
+import androidx.browser.customtabs.CustomTabsServiceConnection
+import androidx.browser.customtabs.CustomTabsSession
 import androidx.lifecycle.lifecycleScope
 import androidx.navigation.findNavController
 import androidx.navigation.ui.AppBarConfiguration
@@ -43,6 +47,7 @@ import kotlinx.coroutines.launch
 import net.underdesk.circolapp.adapters.CircularLetterAdapter
 import net.underdesk.circolapp.data.AndroidDatabase
 import net.underdesk.circolapp.databinding.ActivityMainBinding
+import net.underdesk.circolapp.utils.CustomTabsHelper
 import net.underdesk.circolapp.utils.DownloadableFile
 import net.underdesk.circolapp.works.PollWork
 
@@ -58,6 +63,8 @@ class MainActivity : AppCompatActivity(), CircularLetterAdapter.AdapterCallback
     var refreshCallback: RefreshCallback? = null
     override var fileToDownload: DownloadableFile? = null
 
+    var customTabsSession: CustomTabsSession? = null
+
     override fun onCreate(savedInstanceState: Bundle?) {
         loadDarkTheme()
         super.onCreate(savedInstanceState)
@@ -88,6 +95,26 @@ class MainActivity : AppCompatActivity(), CircularLetterAdapter.AdapterCallback
         }
     }
 
+    override fun onStart() {
+        val connection: CustomTabsServiceConnection = object : CustomTabsServiceConnection() {
+            override fun onCustomTabsServiceConnected(
+                name: ComponentName,
+                client: CustomTabsClient
+            ) {
+                client.warmup(0)
+                customTabsSession = client.newSession(null)
+            }
+
+            override fun onServiceDisconnected(name: ComponentName) {}
+        }
+        CustomTabsClient.bindCustomTabsService(
+            this,
+            CustomTabsHelper.getPreferredCustomTabsPackage(this),
+            connection
+        )
+        super.onStart()
+    }
+
     override fun onCreateOptionsMenu(menu: Menu): Boolean {
         menuInflater.inflate(R.menu.menu_main, menu)
 

app/src/main/java/net/underdesk/circolapp/adapters/AttachmentAdapter.kt

@@ -24,6 +24,7 @@ import android.view.ViewGroup
 import android.widget.ImageButton
 import android.widget.TextView
 import androidx.recyclerview.widget.RecyclerView
+import net.underdesk.circolapp.MainActivity
 import net.underdesk.circolapp.databinding.ItemAttachmentBinding
 import net.underdesk.circolapp.utils.DownloadableFile
 import net.underdesk.circolapp.utils.FileUtils
@@ -31,9 +32,10 @@ import net.underdesk.circolapp.utils.FileUtils
 class AttachmentAdapter(
     private val attachmentsNames: List<String>,
     private val attachmentsUrls: List<String>,
-    private val adapterCallback: CircularLetterAdapter.AdapterCallback
+    private val mainActivity: MainActivity,
 ) :
     RecyclerView.Adapter<AttachmentAdapter.AttachmentViewHolder>() {
+    private val adapterCallback: CircularLetterAdapter.AdapterCallback = mainActivity
     private lateinit var context: Context
 
     inner class AttachmentViewHolder(binding: ItemAttachmentBinding) : RecyclerView.ViewHolder(binding.root) {
@@ -54,7 +56,7 @@ class AttachmentAdapter(
         holder.title.text = attachmentsNames[position]
 
         holder.viewButton.setOnClickListener {
-            FileUtils.viewFile(attachmentsUrls[position], context)
+            FileUtils.viewFile(attachmentsUrls[position], context, mainActivity.customTabsSession)
         }
 
         holder.shareButton.setOnClickListener {

app/src/main/java/net/underdesk/circolapp/adapters/CircularLetterAdapter.kt

@@ -35,6 +35,7 @@ import androidx.recyclerview.widget.RecyclerView
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.launch
 import net.underdesk.circolapp.AlarmBroadcastReceiver
+import net.underdesk.circolapp.MainActivity
 import net.underdesk.circolapp.R
 import net.underdesk.circolapp.data.AndroidDatabase
 import net.underdesk.circolapp.databinding.ItemCircularBinding
@@ -45,11 +46,12 @@ import net.underdesk.circolapp.utils.FileUtils
 
 class CircularLetterAdapter(
     private var circulars: List<Circular>,
-    private val adapterCallback: AdapterCallback,
+    private val mainActivity: MainActivity,
     private val adapterScope: CoroutineScope
 ) :
     RecyclerView.Adapter<CircularLetterAdapter.CircularLetterViewHolder>() {
     private lateinit var context: Context
+    private val adapterCallback: AdapterCallback = mainActivity
     private var collapsedItems = -1
 
     init {
@@ -136,6 +138,12 @@ class CircularLetterAdapter(
             holder.attachmentsList.visibility = View.GONE
             holder.attachmentsList.adapter = null
         } else {
+            FileUtils.preloadFiles(
+                circulars[position].url,
+                circulars[position].attachmentsUrls,
+                mainActivity.customTabsSession
+            )
+
             holder.collapseButton.setImageDrawable(
                 getDrawable(
                     context,
@@ -155,7 +163,7 @@ class CircularLetterAdapter(
                 holder.attachmentsList.adapter = AttachmentAdapter(
                     circulars[position].attachmentsNames,
                     circulars[position].attachmentsUrls,
-                    adapterCallback
+                    mainActivity
                 )
             } else {
                 holder.attachmentsList.adapter = null
@@ -173,7 +181,7 @@ class CircularLetterAdapter(
                 }
             }
 
-            FileUtils.viewFile(circulars[position].url, context)
+            FileUtils.viewFile(circulars[position].url, context, mainActivity.customTabsSession)
         }
 
         holder.shareButton.setOnClickListener {

app/src/main/java/net/underdesk/circolapp/utils/CustomTabsHelper.kt

@@ -0,0 +1,57 @@
+/*
+ * Circolapp
+ * Copyright (C) 2019-2020  Matteo Schiff
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package net.underdesk.circolapp.utils
+
+import android.content.Context
+import android.content.Intent
+import android.content.pm.ResolveInfo
+import android.net.Uri
+
+object CustomTabsHelper {
+    private const val ACTION_CUSTOM_TABS_CONNECTION =
+        "android.support.customtabs.action.CustomTabsService"
+
+    fun getPreferredCustomTabsPackage(context: Context): String {
+        val packages = getCustomTabsPackages(context)
+
+        return if (packages.isEmpty()) "com.android.chrome" else packages[0].activityInfo.packageName
+    }
+
+    private fun getCustomTabsPackages(context: Context): ArrayList<ResolveInfo> {
+        val pm = context.packageManager
+        // Get default VIEW intent handler.
+        val activityIntent = Intent()
+            .setAction(Intent.ACTION_VIEW)
+            .addCategory(Intent.CATEGORY_BROWSABLE)
+            .setData(Uri.fromParts("http", "", null))
+
+        // Get all apps that can handle VIEW intents.
+        val resolvedActivityList = pm.queryIntentActivities(activityIntent, 0)
+        val packagesSupportingCustomTabs: ArrayList<ResolveInfo> = ArrayList()
+        for (info in resolvedActivityList) {
+            val serviceIntent = Intent()
+            serviceIntent.action = ACTION_CUSTOM_TABS_CONNECTION
+            serviceIntent.setPackage(info.activityInfo.packageName)
+            if (pm.resolveService(serviceIntent, 0) != null) {
+                packagesSupportingCustomTabs.add(info)
+            }
+        }
+        return packagesSupportingCustomTabs
+    }
+}

app/src/main/java/net/underdesk/circolapp/utils/FileUtils.kt

@@ -5,9 +5,12 @@ import android.content.Context
 import android.content.Intent
 import android.content.pm.PackageManager
 import android.net.Uri
+import android.os.Bundle
 import androidx.appcompat.app.AppCompatActivity
 import androidx.browser.customtabs.CustomTabColorSchemeParams
 import androidx.browser.customtabs.CustomTabsIntent.*
+import androidx.browser.customtabs.CustomTabsService
+import androidx.browser.customtabs.CustomTabsSession
 import androidx.core.app.ActivityCompat
 import androidx.core.content.ContextCompat
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
@@ -16,7 +19,7 @@ import net.underdesk.circolapp.R
 import net.underdesk.circolapp.adapters.CircularLetterAdapter
 
 object FileUtils {
-    fun viewFile(url: String, context: Context) {
+    fun viewFile(url: String, context: Context, session: CustomTabsSession?) {
         if (url.endsWith(".pdf")) {
             val viewIntent = Intent(Intent.ACTION_VIEW)
             viewIntent.setDataAndType(Uri.parse(url), "application/pdf")
@@ -46,7 +49,7 @@ object FileUtils {
                 .setToolbarColor(primaryColor)
                 .build()
 
-            val customTabsIntent = Builder()
+            val customTabsIntent = Builder(session)
                 .setShowTitle(true)
                 .setColorScheme(COLOR_SCHEME_SYSTEM)
                 .setDefaultColorSchemeParams(otherParams)
@@ -57,6 +60,24 @@ object FileUtils {
         }
     }
 
+    fun preloadFiles(url: String, otherUrls: List<String>, session: CustomTabsSession?) {
+        if (!url.endsWith(".pdf")) {
+            val bundles = arrayListOf<Bundle>()
+
+            for (otherUrl in otherUrls) {
+                if (!url.endsWith(".pdf")) {
+                    val bundle = Bundle().apply {
+                        putParcelable(CustomTabsService.KEY_URL, Uri.parse(otherUrl))
+                    }
+
+                    bundles.add(bundle)
+                }
+            }
+
+            session?.mayLaunchUrl(Uri.parse(url), null, bundles)
+        }
+    }
+
     fun shareFile(url: String, context: Context) {
         val sendIntent: Intent = Intent().apply {
             action = Intent.ACTION_SEND