Implement HTTP proxy summary as a SummaryProvider (#3091)

* Handle preference fragments using the framework

The previous code started new preference "screens" as activities, even though
each one hosted a single fragment.

Modify this to use the framework's support for swapping in/out different
preference fragments.

PreferencesActivity:
- Remove the code for launching tab and proxy preferences
- Remove the code for setting titles, each fragment is responsible for that
- Implement OnPreferenceStartFragmentCallback to swap fragments in/out with
  the correct animation

PreferencesFragment:
- Use `fragment` property instead of `setOnPreferenceClickListener`
- Set the activity title when resuming

Everything else:
- Set the activity title when resuming

* Implement HTTP proxy summary as a SummaryProvider

Uses the frameworks's support for setting summaries instead of rolling our
own.

Also fix a tiny bug -- the minimum port number to connect to should be 1,
not 0.

* Lint

app/src/main/java/com/keylesspalace/tusky/components/preference/PreferencesFragment.kt

@@ -32,7 +32,6 @@ import com.keylesspalace.tusky.settings.preferenceCategory
 import com.keylesspalace.tusky.settings.switchPreference
 import com.keylesspalace.tusky.util.LocaleManager
 import com.keylesspalace.tusky.util.deserialize
-import com.keylesspalace.tusky.util.getNonNullString
 import com.keylesspalace.tusky.util.makeIcon
 import com.keylesspalace.tusky.util.serialize
 import com.mikepenz.iconics.IconicsDrawable
@@ -49,7 +48,6 @@ class PreferencesFragment : PreferenceFragmentCompat(), Injectable {
     lateinit var localeManager: LocaleManager
 
     private val iconSize by lazy { resources.getDimensionPixelSize(R.dimen.preference_icon_size) }
-    private var httpProxyPref: Preference? = null
 
     enum class ReadingOrder {
         /** User scrolls up, reading statuses oldest to newest */
@@ -236,7 +234,7 @@ class PreferencesFragment : PreferenceFragmentCompat(), Injectable {
             preferenceCategory(R.string.pref_title_timeline_filters) {
                 preference {
                     setTitle(R.string.pref_title_post_tabs)
-                    fragment = "com.keylesspalace.tusky.components.preference.TabFilterPreferencesFragment"
+                    fragment = TabFilterPreferencesFragment::class.qualifiedName
                 }
             }
 
@@ -280,9 +278,10 @@ class PreferencesFragment : PreferenceFragmentCompat(), Injectable {
             }
 
             preferenceCategory(R.string.pref_title_proxy_settings) {
-                httpProxyPref = preference {
+                preference {
                     setTitle(R.string.pref_title_http_proxy_settings)
-                    fragment = "com.keylesspalace.tusky.components.preference.ProxyPreferencesFragment"
+                    fragment = ProxyPreferencesFragment::class.qualifiedName
+                    summaryProvider = ProxyPreferencesFragment.SummaryProvider
                 }
             }
         }
@@ -295,28 +294,6 @@ class PreferencesFragment : PreferenceFragmentCompat(), Injectable {
     override fun onResume() {
         super.onResume()
         requireActivity().setTitle(R.string.action_view_preferences)
-        updateHttpProxySummary()
-    }
-
-    private fun updateHttpProxySummary() {
-        preferenceManager.sharedPreferences?.let { sharedPreferences ->
-            val httpProxyEnabled = sharedPreferences.getBoolean(PrefKeys.HTTP_PROXY_ENABLED, false)
-            val httpServer = sharedPreferences.getNonNullString(PrefKeys.HTTP_PROXY_SERVER, "")
-
-            try {
-                val httpPort = sharedPreferences.getNonNullString(PrefKeys.HTTP_PROXY_PORT, "-1")
-                    .toInt()
-
-                if (httpProxyEnabled && httpServer.isNotBlank() && httpPort > 0 && httpPort < 65535) {
-                    httpProxyPref?.summary = "$httpServer:$httpPort"
-                    return
-                }
-            } catch (e: NumberFormatException) {
-                // user has entered wrong port, fall back to empty summary
-            }
-
-            httpProxyPref?.summary = ""
-        }
     }
 
     override fun onDisplayPreferenceDialog(preference: Preference) {

app/src/main/java/com/keylesspalace/tusky/components/preference/ProxyPreferencesFragment.kt

@@ -16,14 +16,18 @@
 package com.keylesspalace.tusky.components.preference
 
 import android.os.Bundle
+import androidx.preference.Preference
 import androidx.preference.PreferenceFragmentCompat
 import com.keylesspalace.tusky.R
 import com.keylesspalace.tusky.settings.PrefKeys
 import com.keylesspalace.tusky.settings.ProxyConfiguration
+import com.keylesspalace.tusky.settings.ProxyConfiguration.Companion.MAX_PROXY_PORT
+import com.keylesspalace.tusky.settings.ProxyConfiguration.Companion.MIN_PROXY_PORT
 import com.keylesspalace.tusky.settings.makePreferenceScreen
 import com.keylesspalace.tusky.settings.preferenceCategory
 import com.keylesspalace.tusky.settings.switchPreference
 import com.keylesspalace.tusky.settings.validatedEditTextPreference
+import com.keylesspalace.tusky.util.getNonNullString
 import kotlin.system.exitProcess
 
 class ProxyPreferencesFragment : PreferenceFragmentCompat() {
@@ -78,6 +82,33 @@ class ProxyPreferencesFragment : PreferenceFragmentCompat() {
         }
     }
 
+    object SummaryProvider : Preference.SummaryProvider<Preference> {
+        override fun provideSummary(preference: Preference): CharSequence {
+            val sharedPreferences = preference.sharedPreferences
+            sharedPreferences ?: return ""
+
+            if (!sharedPreferences.getBoolean(PrefKeys.HTTP_PROXY_ENABLED, false)) {
+                return preference.context.getString(R.string.pref_summary_http_proxy_disabled)
+            }
+
+            val missing = preference.context.getString(R.string.pref_summary_http_proxy_missing)
+
+            val server = sharedPreferences.getNonNullString(PrefKeys.HTTP_PROXY_SERVER, missing)
+            val port = try {
+                sharedPreferences.getNonNullString(PrefKeys.HTTP_PROXY_PORT, "-1").toInt()
+            } catch (e: NumberFormatException) {
+                -1
+            }
+
+            if (port < MIN_PROXY_PORT || port > MAX_PROXY_PORT) {
+                val invalid = preference.context.getString(R.string.pref_summary_http_proxy_invalid)
+                return "$server:$invalid"
+            }
+
+            return "$server:$port"
+        }
+    }
+
     companion object {
         fun newInstance(): ProxyPreferencesFragment {
             return ProxyPreferencesFragment()

app/src/main/java/com/keylesspalace/tusky/settings/ProxyConfiguration.kt

@@ -22,7 +22,7 @@ class ProxyConfiguration private constructor(
         }
         fun isValidHostname(hostname: String): Boolean =
             IP_ADDRESS_REGEX.matches(hostname) || HOSTNAME_REGEX.matches(hostname)
-        const val MIN_PROXY_PORT = 0
+        const val MIN_PROXY_PORT = 1
         const val MAX_PROXY_PORT = 65535
     }
 }

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

@@ -291,6 +291,9 @@
     <string name="pref_title_http_proxy_server">HTTP proxy server</string>
     <string name="pref_title_http_proxy_port">HTTP proxy port</string>
     <string name="pref_title_http_proxy_port_message">Port should be between %d and %d</string>
+    <string name="pref_summary_http_proxy_disabled">Disabled</string>
+    <string name="pref_summary_http_proxy_missing">&lt;not set></string>
+    <string name="pref_summary_http_proxy_invalid">&lt;invalid></string>
 
     <string name="pref_default_post_privacy">Default post privacy</string>
     <string name="pref_default_post_language">Default posting language</string>