86 lines
2.9 KiB
Go
86 lines
2.9 KiB
Go
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// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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/*
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Package app lets you write portable all-Go apps for Android and iOS.
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There are typically two ways to use Go on Android and iOS. The first
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is to write a Go library and use `gomobile bind` to generate language
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bindings for Java and Objective-C. Building a library does not
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require the app package. The `gomobile bind` command produces output
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that you can include in an Android Studio or Xcode project. For more
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on language bindings, see https://golang.org/x/mobile/cmd/gobind.
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The second way is to write an app entirely in Go. The APIs are limited
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to those that are portable between both Android and iOS, in particular
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OpenGL, audio, and other Android NDK-like APIs. An all-Go app should
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use this app package to initialize the app, manage its lifecycle, and
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receive events.
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Building apps
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Apps written entirely in Go have a main function, and can be built
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with `gomobile build`, which directly produces runnable output for
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Android and iOS.
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The gomobile tool can get installed with go get. For reference, see
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https://golang.org/x/mobile/cmd/gomobile.
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For detailed instructions and documentation, see
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https://golang.org/wiki/Mobile.
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Event processing in Native Apps
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The Go runtime is initialized on Android when NativeActivity onCreate is
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called, and on iOS when the process starts. In both cases, Go init functions
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run before the app lifecycle has started.
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An app is expected to call the Main function in main.main. When the function
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exits, the app exits. Inside the func passed to Main, call Filter on every
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event received, and then switch on its type. Registered filters run when the
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event is received, not when it is sent, so that filters run in the same
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goroutine as other code that calls OpenGL.
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package main
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import (
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"log"
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"golang.org/x/mobile/app"
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"golang.org/x/mobile/event/lifecycle"
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"golang.org/x/mobile/event/paint"
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)
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func main() {
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app.Main(func(a app.App) {
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for e := range a.Events() {
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switch e := a.Filter(e).(type) {
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case lifecycle.Event:
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// ...
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case paint.Event:
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log.Print("Call OpenGL here.")
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a.Publish()
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}
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}
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})
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}
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An event is represented by the empty interface type interface{}. Any value can
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be an event. Commonly used types include Event types defined by the following
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packages:
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- golang.org/x/mobile/event/lifecycle
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- golang.org/x/mobile/event/mouse
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- golang.org/x/mobile/event/paint
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- golang.org/x/mobile/event/size
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- golang.org/x/mobile/event/touch
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For example, touch.Event is the type that represents touch events. Other
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packages may define their own events, and send them on an app's event channel.
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Other packages can also register event filters, e.g. to manage resources in
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response to lifecycle events. Such packages should call:
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app.RegisterFilter(etc)
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in an init function inside that package.
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*/
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package app // import "golang.org/x/mobile/app"
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