Properly support predictive back

mobile/src/main/java/com/github/shadowsocks/MainActivity.kt

@@ -26,7 +26,9 @@ import android.os.RemoteException
 import android.view.KeyCharacterMap
 import android.view.KeyEvent
 import android.view.MenuItem
+import android.view.View
 import android.view.ViewGroup
+import androidx.activity.OnBackPressedCallback
 import androidx.appcompat.app.AppCompatActivity
 import androidx.browser.customtabs.CustomTabColorSchemeParams
 import androidx.browser.customtabs.CustomTabsIntent
@@ -54,6 +56,7 @@ import com.google.android.material.snackbar.Snackbar
 import com.google.firebase.analytics.ktx.analytics
 import com.google.firebase.analytics.ktx.logEvent
 import com.google.firebase.ktx.Firebase
+import timber.log.Timber
 
 class MainActivity : AppCompatActivity(), ShadowsocksConnection.Callback, OnPreferenceDataStoreChangeListener,
         NavigationView.OnNavigationItemSelectedListener {
@@ -141,6 +144,21 @@ class MainActivity : AppCompatActivity(), ShadowsocksConnection.Callback, OnPref
         stats = findViewById(R.id.stats)
         stats.setOnClickListener { if (state == BaseService.State.Connected) stats.testConnection() }
         drawer = findViewById(R.id.drawer)
+        val drawerHandler = object : OnBackPressedCallback(drawer.isOpen), DrawerLayout.DrawerListener {
+            override fun handleOnBackPressed() = drawer.closeDrawers()
+            override fun onDrawerSlide(drawerView: View, slideOffset: Float) { }
+            override fun onDrawerOpened(drawerView: View) {
+                isEnabled = true
+            }
+            override fun onDrawerClosed(drawerView: View) {
+                isEnabled = false
+            }
+            override fun onDrawerStateChanged(newState: Int) {
+                isEnabled = newState == DrawerLayout.STATE_IDLE == drawer.isOpen
+            }
+        }
+        onBackPressedDispatcher.addCallback(drawerHandler)
+        drawer.addDrawerListener(drawerHandler)
         navigation = findViewById(R.id.navigation)
         navigation.setNavigationItemSelectedListener(this)
         if (savedInstanceState == null) {
@@ -208,18 +226,6 @@ class MainActivity : AppCompatActivity(), ShadowsocksConnection.Callback, OnPref
         connection.bandwidthTimeout = 500
     }
 
-    override fun onBackPressed() {
-        if (drawer.isDrawerOpen(GravityCompat.START)) drawer.closeDrawers() else {
-            val currentFragment = supportFragmentManager.findFragmentById(R.id.fragment_holder) as ToolbarFragment
-            if (!currentFragment.onBackPressed()) {
-                if (currentFragment is ProfilesFragment) super.onBackPressed() else {
-                    navigation.menu.findItem(R.id.profiles).isChecked = true
-                    displayFragment(ProfilesFragment())
-                }
-            }
-        }
-    }
-
     override fun onKeyShortcut(keyCode: Int, event: KeyEvent) = when {
         keyCode == KeyEvent.KEYCODE_G && event.hasModifiers(KeyEvent.META_CTRL_ON) -> {
             toggle()

mobile/src/main/java/com/github/shadowsocks/ProfileConfigActivity.kt

@@ -25,6 +25,7 @@ import android.content.DialogInterface
 import android.os.Bundle
 import android.view.Menu
 import android.view.MenuItem
+import androidx.activity.OnBackPressedCallback
 import androidx.activity.result.component1
 import androidx.activity.result.component2
 import androidx.activity.result.contract.ActivityResultContracts
@@ -47,6 +48,11 @@ class ProfileConfigActivity : AppCompatActivity() {
     }
 
     private val child by lazy { supportFragmentManager.findFragmentById(R.id.content) as ProfileConfigFragment }
+    val unsavedChangesHandler = object : OnBackPressedCallback(DataStore.dirty) {
+        override fun handleOnBackPressed() = UnsavedChangesDialogFragment().apply {
+            key()
+        }.show(supportFragmentManager, null)
+    }
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -57,6 +63,12 @@ class ProfileConfigActivity : AppCompatActivity() {
             setDisplayHomeAsUpEnabled(true)
             setHomeAsUpIndicator(R.drawable.ic_navigation_close)
         }
+        onBackPressedDispatcher.addCallback(unsavedChangesHandler)
+    }
+
+    override fun onResume() {
+        super.onResume()
+        unsavedChangesHandler.isEnabled = DataStore.dirty
     }
 
     override fun onSupportNavigateUp(): Boolean {
@@ -70,12 +82,6 @@ class ProfileConfigActivity : AppCompatActivity() {
     }
     override fun onOptionsItemSelected(item: MenuItem) = child.onOptionsItemSelected(item)
 
-    override fun onBackPressed() {
-        if (DataStore.dirty) UnsavedChangesDialogFragment().apply {
-            key()
-        }.show(supportFragmentManager, null) else super.onBackPressed()
-    }
-
     val pluginHelp = registerForActivityResult(ActivityResultContracts.StartActivityForResult()) {
         (resultCode, data) ->
         if (resultCode == Activity.RESULT_OK) AlertDialog.Builder(this)

mobile/src/main/java/com/github/shadowsocks/ProfileConfigFragment.kt

@@ -80,6 +80,11 @@ class ProfileConfigFragment : PreferenceFragmentCompat(),
     private lateinit var receiver: BroadcastReceiver
     private lateinit var udpFallback: Preference
 
+    private fun makeDirt() {
+        DataStore.dirty = true
+        (activity as ProfileConfigActivity).unsavedChangesHandler.isEnabled = true
+    }
+
     override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
         preferenceManager.preferenceDataStore = DataStore.privateStore
         val activity = requireActivity()
@@ -97,7 +102,7 @@ class ProfileConfigFragment : PreferenceFragmentCompat(),
         isProxyApps.isEnabled = serviceMode == Key.modeVpn
         isProxyApps.setOnPreferenceChangeListener { _, newValue ->
             startActivity(Intent(activity, AppManager::class.java))
-            if (newValue as Boolean) DataStore.dirty = true
+            if (newValue as Boolean) makeDirt()
             newValue
         }
         findPreference<Preference>(Key.metered)!!.apply {
@@ -136,7 +141,7 @@ class ProfileConfigFragment : PreferenceFragmentCompat(),
             }
             pluginConfiguration = PluginConfiguration(pluginConfiguration.pluginsOptions, override ?: selected.id)
             DataStore.plugin = pluginConfiguration.toString()
-            DataStore.dirty = true
+            makeDirt()
             plugin.value = pluginConfiguration.selected
             pluginConfigure.isEnabled = selected !is NoPlugin
             pluginConfigure.text = pluginConfiguration.getOptions().toString()
@@ -199,15 +204,15 @@ class ProfileConfigFragment : PreferenceFragmentCompat(),
         pluginConfiguration = PluginConfiguration(pluginConfiguration.pluginsOptions +
                 (pluginConfiguration.selected to PluginOptions(selected, newValue as? String?)), selected)
         DataStore.plugin = pluginConfiguration.toString()
-        DataStore.dirty = true
+        makeDirt()
         true
     } catch (exc: RuntimeException) {
         Snackbar.make(requireView(), exc.readableMessage, Snackbar.LENGTH_LONG).show()
         false
     }
 
     override fun onPreferenceDataStoreChanged(store: PreferenceDataStore, key: String) {
-        if (key != Key.proxyApps && findPreference<Preference>(key) != null) DataStore.dirty = true
+        if (key != Key.proxyApps && findPreference<Preference>(key) != null) makeDirt()
     }
 
     override fun onDisplayPreferenceDialog(preference: Preference) {

mobile/src/main/java/com/github/shadowsocks/ToolbarFragment.kt

@@ -35,6 +35,4 @@ open class ToolbarFragment : Fragment() {
         toolbar.setNavigationIcon(R.drawable.ic_navigation_menu)
         toolbar.setNavigationOnClickListener { (activity as MainActivity).drawer.openDrawer(GravityCompat.START) }
     }
-
-    open fun onBackPressed(): Boolean = false
 }

mobile/src/main/java/com/github/shadowsocks/acl/CustomRulesFragment.kt

@@ -21,6 +21,7 @@
 package com.github.shadowsocks.acl
 
 import android.annotation.SuppressLint
+import android.content.Context
 import android.content.DialogInterface
 import android.os.Bundle
 import android.os.Parcelable
@@ -31,6 +32,7 @@ import android.widget.AdapterView
 import android.widget.EditText
 import android.widget.Spinner
 import android.widget.TextView
+import androidx.activity.OnBackPressedCallback
 import androidx.appcompat.app.AlertDialog
 import androidx.appcompat.widget.Toolbar
 import androidx.core.content.ContextCompat
@@ -371,7 +373,10 @@ class CustomRulesFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener,
     private lateinit var undoManager: UndoSnackbarManager<Any>
 
     private fun onSelectedItemsUpdated() {
-        if (selectedItems.isEmpty()) mode?.finish() else if (mode == null) mode = toolbar.startActionMode(this)
+        if (selectedItems.isEmpty()) mode?.finish() else if (mode == null) {
+            mode = toolbar.startActionMode(this)
+            backHandler.isEnabled = true
+        }
     }
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? =
@@ -418,12 +423,15 @@ class CustomRulesFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener,
         }).attachToRecyclerView(list)
     }
 
-    override fun onBackPressed(): Boolean {
-        val mode = mode
-        return if (mode != null) {
-            mode.finish()
-            true
-        } else super.onBackPressed()
+    private val backHandler = object : OnBackPressedCallback(false) {
+        override fun handleOnBackPressed() {
+            mode?.finish()
+        }
+    }
+
+    override fun onAttach(context: Context) {
+        super.onAttach(context)
+        requireActivity().onBackPressedDispatcher.addCallback(backHandler)
     }
 
     override fun onSaveInstanceState(outState: Bundle) {
@@ -477,6 +485,7 @@ class CustomRulesFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener,
     }
 
     override fun onDetach() {
+        backHandler.remove()
         undoManager.flush()
         mode?.finish()
         super.onDetach()
@@ -518,6 +527,7 @@ class CustomRulesFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener,
         selectedItems.clear()
         onSelectedItemsUpdated()
         adapter.notifyDataSetChanged()
+        backHandler.isEnabled = false
         this.mode = null
     }
 }

mobile/src/main/java/com/github/shadowsocks/subscription/SubscriptionFragment.kt

@@ -27,7 +27,10 @@ import android.os.Bundle
 import android.os.Parcelable
 import android.text.Editable
 import android.text.TextWatcher
-import android.view.*
+import android.view.LayoutInflater
+import android.view.MenuItem
+import android.view.View
+import android.view.ViewGroup
 import android.widget.AdapterView
 import android.widget.EditText
 import android.widget.TextView
@@ -115,8 +118,7 @@ class SubscriptionFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener
         }
     }
 
-    private inner class SubViewHolder(view: View) : RecyclerView.ViewHolder(view),
-            View.OnClickListener {
+    private inner class SubViewHolder(view: View) : RecyclerView.ViewHolder(view), View.OnClickListener {
         lateinit var item: URL
         private val text = view.findViewById<TextView>(android.R.id.text1)
 
@@ -197,7 +199,6 @@ class SubscriptionFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener
 
     private val adapter by lazy { SubscriptionAdapter() }
     private lateinit var list: RecyclerView
-    private var mode: ActionMode? = null
     private lateinit var undoManager: UndoSnackbarManager<URL>
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? =
@@ -238,14 +239,6 @@ class SubscriptionFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener
         }).attachToRecyclerView(list)
     }
 
-    override fun onBackPressed(): Boolean {
-        val mode = mode
-        return if (mode != null) {
-            mode.finish()
-            true
-        } else super.onBackPressed()
-    }
-
     override fun onMenuItemClick(item: MenuItem): Boolean = when (item.itemId) {
         R.id.action_manual_settings -> {
             SubDialogFragment().apply {
@@ -264,7 +257,6 @@ class SubscriptionFragment : ToolbarFragment(), Toolbar.OnMenuItemClickListener
 
     override fun onDetach() {
         undoManager.flush()
-        mode?.finish()
         super.onDetach()
     }
 }