SweetJuice Docs

Sweet Juice is an open-source Go framework for building native mobile apps with Material You design, deep system integrations, and a plugin-based architecture powered by gomobile.

Native UI — Declarative widgets in Go, rendered as native Android views via the mu3 plugin.
Material You — All built-in components use Material 3 dynamic color theming.
Plugin system — First-party plugins for permissions, notifications, biometrics, files, and more.
Cross-platform — Android and iOS from a single Go codebase.

Overview

Version: 1.6 Sweet Juice is an open-source Go mobile app development framework for building native mobile apps using Go and native Android/iOS components, powered by gomobile. Features Fast and optimised compile times. Deep Native integrations. Supports cross-platform builds for Android apps on Linux, Windows and macOS. Supports cross-platform builds for iOS apps on Linux, Windows and macOS. GET STARTED WITH TUTORIALS WITH THE BUTTON BELOW

Getting started

This document contains the installation, bootstrapping, build and uninstall steps used during development. Prerequisites Go 1.24+ Android SDK and Android NDK installed (Android Studio recommended) xtool.sh (For cross-platform iOS builds) git, curl NB: For less mess, do not alter the default location for Android SDK. Installation You can use Go to install Sweet Juice CLI tool, juice. Using Go: go install github.com/sweet-juice/sweetjuice/cmd/juice@latest Create a new project juice --new my-new-app This scaffolds a fresh project from the local AppTemplate included in the Sweet Juice module. ...

Build Your First App

1. Scaffold juice --new MyApp cd MyApp 2. Define state lib/state/app_state.go package state type MainAppState struct { SelectedTab string } func NewMainAppState() *MainAppState { return &MainAppState{SelectedTab: "feed"} } func (s *MainAppState) SetSelectedTab(tab string) { s.SelectedTab = tab } 3. Build the UI lib/views/home_view.go package views import ( "myapp/lib/state" "github.com/sweet-juice/sweetjuice/plugins/mu3" "github.com/sweet-juice/sweetjuice/ui" "github.com/sweet-juice/sweetjuice/ui/style" ) type HomeView struct { State *state.MainAppState } func (v *HomeView) Render() ui.Node { return ui.Root( ui.VStack( mu3.TopAppBar("Feed", "menu"), ui.Spacer().Height(12), mu3.SearchBar("Search...", false), ui.Spacer().Height(16), mu3.Tabs([]string{"For You", "Saved", "Archived"}, nil, v.State.SelectedTab). OnChanged(v.State.SetSelectedTab), ui.Spacer().Height(16), v.contentForTab(), ui.Spacer().Height(24), mu3.NavigationBar([]map[string]string{ {"label": "Home", "icon": "home"}, {"label": "Explore", "icon": "explore"}, {"label": "Profile", "icon": "person"}, }), ), "#FFFBFE", ) } func (v *HomeView) contentForTab() ui.Node { switch v.State.SelectedTab { case "saved": return ui.VStack( mu3.Card("Saved", "Item 1").OnClick(func() { println("saved") }), ui.Spacer().Height(12), mu3.Card("Saved", "Item 2").OnClick(func() { println("saved") }), ) default: return ui.VStack( mu3.Card("Feed", "Welcome to Sweet Juice").OnClick(func() { println("feed") }), ui.Spacer().Height(12), mu3.Card("Feed", "Material You is active").OnClick(func() { println("feed") }), ) } } 4. Bootstrap start.go ...

Plugins

Sweet Juice plugins are first-party bridges between Go and native Android system APIs. Plugin guides Permissions Plugin — Check and request runtime permissions. Notification Plugin — Post and cancel system notifications. Calls Plugin — Read device call history. SMS Plugin — Read SMS messages from inbox, sent, and drafts. WorkManager Plugin — Schedule background tasks. Special Permissions Plugin — Accessibility, battery exemption, notification access, and more. Notification Listener Plugin — React to notifications posted or removed by any app. DataDir Plugin — Read/write app internal storage and access standard directories. More plugins are documented as they are stabilized and stress-tested. ...

Writing Plugins

A Sweet Juice plugin has two parts: Go side — exposes a friendly API and calls core.CallNativePlatform to reach native code. Native side — implements SweetJuicePlugin, registers widget factories, and handles actions. Go-side plugin package myplugin import ( "encoding/json" "github.com/sweet-juice/sweetjuice/core" ) type Plugin struct { app *core.Application } func NewPlugin() *Plugin { return &Plugin{} } func (p *Plugin) Init(app *core.Application) error { p.app = app // Register native callbacks if needed app.RegisterNativeMethod("myplugin:result", func(args []json.RawMessage) (interface{}, error) { // handle result from native side return map[string]string{"status": "ok"}, nil }) return nil } func (p *Plugin) DoSomething(input string) (string, error) { payload, _ := json.Marshal(map[string]string{"input": input}) return core.CallNativePlatform("myplugin:doSomething", payload), nil } Native-side plugin (Android) package com.sweetjuice.pkg.myplugin; import android.content.Context; import com.sweetjuice.plugin.SweetJuicePlugin; import org.json.JSONObject; import org.json.JSONException; public class MyPlugin implements SweetJuicePlugin { private Context mContext; @Override public String getDomain() { return "myplugin"; } @Override public void onAttach(Context context) { this.mContext = context; } @Override public String handleAction(String action, String jsonArgsPayload) { try { JSONObject args = new JSONObject(jsonArgsPayload); if ("doSomething".equals(action)) { String input = args.optString("input", ""); // do native work return "{\"result\":\"" + input + "\"}"; } return "{\"error\":\"Unknown action\"}"; } catch (JSONException e) { return "{\"error\":\"" + e.getMessage() + "\"}"; } } } Register the plugin Add the plugin to SweetJuiceApplication: ...

Notification Plugin

The Notification plugin lets your app post and cancel system notifications on Android. Setup The notification plugin is already registered in the default AppTemplate. Android Manifest <uses-permission android:name="android.permission.POST_NOTIFICATIONS" /> API notification.NewPlugin() *NotificationPlugin Creates a new notification plugin instance. (*NotificationPlugin).Post(n Notification) (string, error) Posts a system notification. Returns: A result string from the native layer, typically {"status":"posted"} or similar. (*NotificationPlugin).Cancel(id int) string Cancels a previously posted notification by its ID. Types Notification type Notification struct { ID int `json:"id"` Title string `json:"title"` Body string `json:"body"` ChannelID string `json:"channel_id"` ChannelName string `json:"channel_name"` Importance Importance `json:"importance"` } Field Description ID Notification ID. If 0, a unique ID is generated automatically Title Notification title text Body Notification body text ChannelID Android notification channel ID. Defaults to default_channel ChannelName Human-readable channel name. Defaults to General Notifications Importance Notification priority level Importance type Importance string const ( ImportanceDefault Importance = "DEFAULT" ImportanceHigh Importance = "HIGH" ImportanceLow Importance = "LOW" ImportanceMin Importance = "MIN" ) Example import "github.com/sweet-juice/sweetjuice/plugins/notification" plugin := notification.NewPlugin() _, err := plugin.Post(notification.Notification{ Title: "Sweet Juice", Body: "Background sync running...", ChannelID: "default_channel", ChannelName: "General Notifications", Importance: notification.ImportanceDefault, }) // Cancel a notification by ID plugin.Cancel(12345) Notes On Android 13+ (API 33), the user must grant POST_NOTIFICATIONS runtime permission before notifications can be posted. The notification plugin uses a default channel if none is specified. Custom channels should be created natively if you need different behavior.

Writing Android Plugins

Android plugins live under: plugins/<name>/android/com/sweetjuice/pkg/<name>/ And are synced into the template at: AppTemplate/native/android/app/src/main/java/com/sweetjuice/pkg/<name>/ Plugin contract Every plugin must implement SweetJuicePlugin: public class MyPlugin implements SweetJuicePlugin { @Override public String getDomain() { return "mydomain"; } @Override public void onAttach(Context context) { } @Override public String handleAction(String action, String jsonArgsPayload) { // route action to handler return "{}"; } } Action routing handleAction receives the action name and a JSON payload. Use it to route to specific handlers: @Override public String handleAction(String action, String jsonArgsPayload) { try { JSONObject args = new JSONObject(jsonArgsPayload); switch (action) { case "check": return check(args); case "request": return request(args); default: return errorJson("Unknown action"); } } catch (JSONException e) { return errorJson(e.getMessage()); } } Returning results Return JSON strings. The Go side receives the raw string and unmarshals it: ...

Calls Plugin

The Calls plugin provides read-only access to the device call log. Setup The calls plugin is already registered in the default AppTemplate. Android Manifest <uses-permission android:name="android.permission.READ_CALL_LOG" /> API calls.GetRecent(limit int) (CallLog, error) Fetches the most recent call log entries. Returns: CallLog containing Calls and Count calls.GetLast(limit int) (CallLog, error) An alias for GetRecent(limit). calls.GetAll() (CallLog, error) Fetches the entire call log. Returns: CallLog or error Types CallLog type CallLog struct { Calls []CallRecord `json:"calls"` Count int `json:"count"` } CallRecord Field Type Description ID int64 Stable row ID Number string Phone number or URI Type string "incoming", "outgoing", "missed", etc. Date int64 Epoch millis Duration int64 Duration in seconds CachedName string Contact name if available GeoLocation string Reverse-geocoded location if available Events calls:changed Emitted when the native side detects a call-log change. ...

Permissions Plugin

The Permissions plugin provides a thin, reliable bridge between Go and the Android runtime permission system. Setup The permissions plugin is already registered in the default AppTemplate. API permission.Check(permission string) (string, error) Returns the current status of a single permission. permission.Request(permission string) (string, error) Shows the system permission dialog. permission.RequestMultiple(permissions []string) (string, error) Requests multiple permissions sequentially. Events permissions:changed Emitted each time a permission request completes. { "permission": "android.permission.READ_CALL_LOG", "granted": true } Example import "github.com/sweet-juice/sweetjuice/plugins/permission" status, _ := permission.RequestMultiple([]string{ "android.permission.READ_CALL_LOG", "android.permission.READ_SMS", })

SMS Plugin

The SMS plugin provides read-only access to device SMS messages across inbox, sent, and draft folders. Setup The SMS plugin is already registered in the default AppTemplate. Android Manifest <uses-permission android:name="android.permission.READ_SMS" /> Note: On Android 4.4+ (KITKAT), this plugin can only read SMS messages if your app is the default SMS app. API sms.GetRecent(limit int) (SmsFolder, error) Fetches the most recent SMS messages across all folders. Returns: SmsFolder or error ...