Add a hint for an empty app list

app/src/main/java/io/nekohasekai/sagernet/ui/AppListActivity.kt

@@ -2,7 +2,6 @@ package io.nekohasekai.sagernet.ui
 
 import android.content.Intent
 import android.content.pm.ApplicationInfo
-import android.content.pm.PackageInfo
 import android.content.pm.PackageManager
 import android.graphics.drawable.Drawable
 import android.os.Bundle
@@ -45,6 +44,11 @@ import kotlin.coroutines.coroutineContext
 class AppListActivity : ThemedActivity() {
     companion object {
         private const val SWITCH = "switch"
+
+        private val cachedApps
+            get() = PackageCache.installedPackages.toMutableMap().apply {
+                remove(BuildConfig.APPLICATION_ID)
+            }
     }
 
     private class ProxiedApp(
@@ -96,7 +100,7 @@ class AppListActivity : ThemedActivity() {
         var filteredApps = apps
 
         suspend fun reload() {
-            apps = getCachedApps().mapNotNull { (packageName, packageInfo) ->
+            apps = cachedApps.mapNotNull { (packageName, packageInfo) ->
                 coroutineContext[Job]!!.ensureActive()
                 packageInfo.applicationInfo?.let { ProxiedApp(packageManager, it, packageName) }
             }.sortedWith(compareBy({ !isProxiedApp(it) }, { it.name.toString() }))
@@ -156,7 +160,7 @@ class AppListActivity : ThemedActivity() {
 
     private fun initProxiedUids(str: String = DataStore.routePackages) {
         proxiedUids.clear()
-        val apps = getCachedApps()
+        val apps = cachedApps
         for (line in str.lineSequence()) {
             val app = (apps[line] ?: continue)
             val uid = app.applicationInfo?.uid ?: continue
@@ -174,15 +178,13 @@ class AppListActivity : ThemedActivity() {
             val adapter = binding.list.adapter as AppsAdapter
             withContext(Dispatchers.IO) { adapter.reload() }
             adapter.filter.filter(binding.search.text?.toString() ?: "")
+            if (apps.isEmpty()) {
+                binding.list.visibility = View.GONE
+                binding.appPlaceholder.root.crossFadeFrom(loading)
+            } else {
                 binding.list.crossFadeFrom(loading)
             }
         }
-
-    fun getCachedApps(): MutableMap<String, PackageInfo> {
-        val packages = PackageCache.installedPackages
-        return packages.toMutableMap().apply {
-            remove(BuildConfig.APPLICATION_ID)
-        }
     }
 
     override fun onCreate(savedInstanceState: Bundle?) {
@@ -191,6 +193,14 @@ class AppListActivity : ThemedActivity() {
         binding = LayoutAppListBinding.inflate(layoutInflater)
         setContentView(binding.root)
 
+        binding.appPlaceholder.openSettings.setOnClickListener {
+            val intent =
+                Intent(android.provider.Settings.ACTION_APPLICATION_DETAILS_SETTINGS).apply {
+                    data = android.net.Uri.fromParts("package", packageName, null)
+                }
+            startActivity(intent)
+        }
+
         setSupportActionBar(binding.toolbar)
         supportActionBar?.apply {
             setTitle(R.string.select_apps)

app/src/main/java/io/nekohasekai/sagernet/ui/AppManagerActivity.kt

@@ -184,9 +184,14 @@ class AppManagerActivity : ThemedActivity() {
             val adapter = binding.list.adapter as AppsAdapter
             withContext(Dispatchers.IO) { adapter.reload() }
             adapter.filter.filter(binding.search.text?.toString() ?: "")
+            if (apps.isEmpty()) {
+                binding.list.visibility = View.GONE
+                binding.appPlaceholder.root.crossFadeFrom(loading)
+            } else {
                 binding.list.crossFadeFrom(loading)
             }
         }
+    }
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -194,6 +199,14 @@ class AppManagerActivity : ThemedActivity() {
         binding = LayoutAppsBinding.inflate(layoutInflater)
         setContentView(binding.root)
 
+        binding.appPlaceholder.openSettings.setOnClickListener {
+            val intent =
+                Intent(android.provider.Settings.ACTION_APPLICATION_DETAILS_SETTINGS).apply {
+                    data = android.net.Uri.fromParts("package", packageName, null)
+                }
+            startActivity(intent)
+        }
+
         setSupportActionBar(binding.toolbar)
         supportActionBar?.apply {
             setTitle(R.string.proxied_apps)

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

@@ -116,4 +116,8 @@
         app:layout_behavior="@string/appbar_scrolling_view_behavior"
         tools:listitem="@layout/layout_apps_item" />
 
+    <include
+        android:id="@+id/app_placeholder"
+        layout="@layout/layout_app_placeholder" />
+
 </androidx.coordinatorlayout.widget.CoordinatorLayout>

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

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:gravity="center"
+    android:orientation="vertical"
+    android:padding="32dp"
+    android:visibility="gone">
+
+    <TextView
+        android:id="@+id/empty_message"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:gravity="center"
+        android:paddingBottom="16dp"
+        android:text="@string/app_list_permission_denied"
+        android:textColor="?attr/colorOnBackground"
+        android:textSize="16sp" />
+
+    <com.google.android.material.button.MaterialButton
+        android:id="@+id/open_settings"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="@string/open_app_settings" />
+</LinearLayout>

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

@@ -153,4 +153,8 @@
         app:layout_behavior="@string/appbar_scrolling_view_behavior"
         tools:listitem="@layout/layout_apps_item" />
 
+    <include
+        android:id="@+id/app_placeholder"
+        layout="@layout/layout_app_placeholder" />
+
 </androidx.coordinatorlayout.widget.CoordinatorLayout>

app/src/main/res/values-zh-rCN/strings.xml

@@ -495,4 +495,6 @@
     <string name="reset_settings">恢复默认设置</string>
     <string name="reset_settings_message">恢复默认设置，但节点、分组等数据将保留。如需完全清除数据，请在系统设置中直接清除应用数据。</string>
     <string name="minimize">最小化</string>
+    <string name="app_list_permission_denied">无法读取已安装的应用。\n这通常是由于系统限制了应用的读取权限（例如某些中国厂商系统）。\n请在系统设置中授予权限。</string>
+    <string name="open_app_settings">打开系统设置</string>
 </resources>

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

@@ -575,4 +575,6 @@
     <string name="reset_settings">Restore default settings</string>
     <string name="reset_settings_message">Restore default settings, but data such as nodes and groups will be retained. To completely clear data, clear application data directly in the system settings.</string>
     <string name="minimize">Minimize</string>
+    <string name="app_list_permission_denied">Unable to read installed apps.\nThis is usually because the system has restricted app read permissions.\nPlease grant permissions in the system settings.</string>
+    <string name="open_app_settings">Open System Settings</string>
 </resources>