Add a button for installing OpenTasks if not already installed.

app/src/main/java/com/etesync/syncadapter/ui/AccountActivity.kt

@@ -13,6 +13,7 @@ import android.accounts.AccountManager
 import android.app.LoaderManager
 import android.content.*
 import android.content.ContentResolver.SYNC_OBSERVER_TYPE_ACTIVE
+import android.net.Uri
 import android.os.Build
 import android.os.Bundle
 import android.os.IBinder
@@ -38,6 +39,7 @@ import com.etesync.syncadapter.resource.LocalCalendar
 import com.etesync.syncadapter.ui.setup.SetupUserInfoFragment
 import com.etesync.syncadapter.utils.HintManager
 import com.etesync.syncadapter.utils.ShowcaseBuilder
+import com.etesync.syncadapter.utils.packageInstalled
 import tourguide.tourguide.ToolTip
 import java.util.logging.Level
 
@@ -101,6 +103,29 @@ class AccountActivity : BaseActivity(), Toolbar.OnMenuItemClickListener, PopupMe
         tbTaskDAV.inflateMenu(R.menu.taskdav_actions)
         tbTaskDAV.setOnMenuItemClickListener(this)
         tbTaskDAV.setTitle(R.string.settings_taskdav)
+        val openTasksPackage = "org.dmfs.tasks"
+        if (!packageInstalled(this, openTasksPackage)) {
+            val tasksInstallButton = findViewById<LinearLayout>(R.id.taskdav_install_button)
+            tasksInstallButton.visibility = View.VISIBLE
+            tasksInstallButton.setOnClickListener {
+                val fdroidPackageName = "org.fdroid.fdroid"
+                val gplayPackageName = "com.android.vending"
+                val intent = Intent(Intent.ACTION_VIEW).apply {
+                    data = Uri.parse(
+                            "https://f-droid.org/en/packages/$openTasksPackage/")
+                }
+                if (packageInstalled(this, fdroidPackageName)) {
+                    intent.setPackage(fdroidPackageName)
+                } else if (packageInstalled(this, gplayPackageName)) {
+                    intent.apply {
+                        data = Uri.parse(
+                                "https://play.google.com/store/apps/details?id=$openTasksPackage")
+                        setPackage(gplayPackageName)
+                    }
+                }
+                startActivity(intent)
+            }
+        }
 
         // load CardDAV/CalDAV journals
         loaderManager.initLoader(0, intent.extras, this)

app/src/main/res/layout/activity_account.xml

@@ -128,8 +128,28 @@
                     style="@style/Widget.AppCompat.ProgressBar.Horizontal"
                     android:layout_width="match_parent"
                     android:layout_height="wrap_content"
+                    android:indeterminate="true"
+                    android:visibility="gone" />
+
+                <LinearLayout
+                    android:id="@+id/taskdav_install_button"
                     android:visibility="gone"
-                    android:indeterminate="true"/>
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:gravity="center_vertical"
+                    android:orientation="horizontal"
+                    android:paddingLeft="12dp"
+                    android:paddingTop="8dp"
+                    android:paddingRight="12dp"
+                    android:paddingBottom="8dp">
+
+                    <TextView
+                        android:text="@string/account_click_install_tasks"
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:textAppearance="?android:attr/textAppearanceMedium" />
+
+                </LinearLayout>
 
                 <com.etesync.syncadapter.ui.widget.MaximizedListView
                     android:id="@+id/tasklists"

app/src/main/res/values/strings.xml

@@ -115,6 +115,7 @@
     <string name="account_delete_collection_last_title">Can\'t delete last collection</string>
     <string name="account_delete_collection_last_text">Deleting the last collection is not allowed, please create a new one if you\'d like to delete this one.</string>
     <string name="account_showcase_view_collection">You can click on an item to view the collection. From there you can view the journal, import, and much more...</string>
+    <string name="account_click_install_tasks">Click here to install OpenTasks!</string>
 
     <string name="show_fingperprint_title">My Fingerprint</string>