cmd/gomobile/bind_androidapp.go

// Copyright 2015 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"archive/zip"
	"bytes"
	"fmt"
	"go/build"
	"io"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"text/template"
)

func goAndroidBind(pkg *build.Package) error {
	if sdkDir := os.Getenv("ANDROID_HOME"); sdkDir == "" {
		return fmt.Errorf("this command requires ANDROID_HOME environment variable (path to the Android SDK)")
	}

	binder, err := newBinder(pkg)
	if err != nil {
		return err
	}

	if err := binder.GenGo(tmpdir); err != nil {
		return err
	}

	mainFile := filepath.Join(tmpdir, "androidlib/main.go")
	err = writeFile(mainFile, func(w io.Writer) error {
		return androidMainTmpl.Execute(w, "../go_"+binder.pkg.Name())
	})
	if err != nil {
		return fmt.Errorf("failed to create the main package for android: %v", err)
	}

	androidDir := filepath.Join(tmpdir, "android")

	err = goBuild(
		mainFile,
		androidArmEnv,
		"-buildmode=c-shared",
		"-o="+filepath.Join(androidDir, "src/main/jniLibs/armeabi-v7a/libgojni.so"),
	)
	if err != nil {
		return err
	}

	p, err := ctx.Import("golang.org/x/mobile/bind", cwd, build.ImportComment)
	if err != nil {
		return fmt.Errorf(`"golang.org/x/mobile/bind" is not found; run go get golang.org/x/mobile/bind`)
	}
	repo := filepath.Clean(filepath.Join(p.Dir, "..")) // golang.org/x/mobile directory.

	// TODO(crawshaw): use a better package path derived from the go package.
	if err := binder.GenJava(filepath.Join(androidDir, "src/main/java/go/"+binder.pkg.Name())); err != nil {
		return err
	}

	dst := filepath.Join(androidDir, "src/main/java/go/LoadJNI.java")
	if err := ioutil.WriteFile(dst, []byte(loadSrc), 0664); err != nil {
		return err
	}

	src := filepath.Join(repo, "bind/java/Seq.java")
	dst = filepath.Join(androidDir, "src/main/java/go/Seq.java")
	rm(dst)
	if err := symlink(src, dst); err != nil {
		return err
	}

	return buildAAR(androidDir, pkg)
}

var loadSrc = `package go;

public class LoadJNI {
	static {
		System.loadLibrary("gojni");
	}
}
`

var androidMainTmpl = template.Must(template.New("android.go").Parse(`
package main

import (
	_ "golang.org/x/mobile/bind/java"
	_ "{{.}}"
)

func main() {}
`))

// AAR is the format for the binary distribution of an Android Library Project
// and it is a ZIP archive with extension .aar.
// http://tools.android.com/tech-docs/new-build-system/aar-format
//
// These entries are directly at the root of the archive.
//
//	AndroidManifest.xml (mandatory)
// 	classes.jar (mandatory)
//	assets/ (optional)
//	jni/<abi>/libgojni.so
//	R.txt (mandatory)
//	res/ (mandatory)
//	libs/*.jar (optional, not relevant)
//	proguard.txt (optional)
//	lint.jar (optional, not relevant)
//	aidl (optional, not relevant)
//
// javac and jar commands are needed to build classes.jar.
func buildAAR(androidDir string, pkg *build.Package) (err error) {
	var out io.Writer = ioutil.Discard
	if buildO == "" {
		buildO = pkg.Name + ".aar"
	}
	if !strings.HasSuffix(buildO, ".aar") {
		return fmt.Errorf("output file name %q does not end in '.aar'", buildO)
	}
	if !buildN {
		f, err := os.Create(buildO)
		if err != nil {
			return err
		}
		defer func() {
			if cerr := f.Close(); err == nil {
				err = cerr
			}
		}()
		out = f
	}

	aarw := zip.NewWriter(out)
	aarwcreate := func(name string) (io.Writer, error) {
		if buildV {
			fmt.Fprintf(os.Stderr, "aar: %s\n", name)
		}
		return aarw.Create(name)
	}
	w, err := aarwcreate("AndroidManifest.xml")
	if err != nil {
		return err
	}
	const manifestFmt = `<manifest xmlns:android="http://schemas.android.com/apk/res/android" package=%q />`
	fmt.Fprintf(w, manifestFmt, "go."+pkg.Name+".gojni")

	w, err = aarwcreate("proguard.txt")
	if err != nil {
		return err
	}
	fmt.Fprintln(w, `-keep class go.** { *; }`)

	w, err = aarwcreate("classes.jar")
	if err != nil {
		return err
	}
	src := filepath.Join(androidDir, "src/main/java")
	if err := buildJar(w, src); err != nil {
		return err
	}

	assetsDir := filepath.Join(pkg.Dir, "assets")
	assetsDirExists := false
	if fi, err := os.Stat(assetsDir); err == nil {
		assetsDirExists = fi.IsDir()
	} else if !os.IsNotExist(err) {
		return err
	}

	if assetsDirExists {
		err := filepath.Walk(
			assetsDir, func(path string, info os.FileInfo, err error) error {
				if err != nil {
					return err
				}
				if info.IsDir() {
					return nil
				}
				f, err := os.Open(path)
				if err != nil {
					return err
				}
				defer f.Close()
				name := "assets/" + path[len(assetsDir)+1:]
				w, err := aarwcreate(name)
				if err != nil {
					return nil
				}
				_, err = io.Copy(w, f)
				return err
			})
		if err != nil {
			return err
		}
	}

	lib := "armeabi-v7a/libgojni.so"
	w, err = aarwcreate("jni/" + lib)
	if err != nil {
		return err
	}
	if !buildN {
		r, err := os.Open(filepath.Join(androidDir, "src/main/jniLibs/"+lib))
		if err != nil {
			return err
		}
		defer r.Close()
		if _, err := io.Copy(w, r); err != nil {
			return err
		}
	}

	// TODO(hyangah): do we need to use aapt to create R.txt?
	w, err = aarwcreate("R.txt")
	if err != nil {
		return err
	}

	w, err = aarwcreate("res/")
	if err != nil {
		return err
	}

	return aarw.Close()
}

const (
	javacTargetVer = "1.7"
	minAndroidAPI  = 9
)

func buildJar(w io.Writer, srcDir string) error {
	var srcFiles []string
	if buildN {
		srcFiles = []string{"*.java"}
	} else {
		err := filepath.Walk(srcDir, func(path string, info os.FileInfo, err error) error {
			if err != nil {
				return err
			}
			if filepath.Ext(path) == ".java" {
				srcFiles = append(srcFiles, filepath.Join(".", path[len(srcDir):]))
			}
			return nil
		})
		if err != nil {
			return err
		}
	}

	dst := filepath.Join(tmpdir, "javac-output")
	if !buildN {
		if err := os.MkdirAll(dst, 0700); err != nil {
			return err
		}
	}
	defer removeAll(dst)

	apiPath, err := androidAPIPath()
	if err != nil {
		return err
	}

	args := []string{
		"-d", dst,
		"-source", javacTargetVer,
		"-target", javacTargetVer,
		"-bootclasspath", filepath.Join(apiPath, "android.jar"),
	}
	args = append(args, srcFiles...)

	buf := new(bytes.Buffer)
	javac := exec.Command("javac", args...)
	javac.Dir = srcDir
	if buildV {
		javac.Stdout = os.Stdout
		javac.Stderr = os.Stderr
	} else {
		javac.Stdout = buf
		javac.Stderr = buf
	}
	if buildX {
		printcmd("%s", strings.Join(javac.Args, " "))
	}
	if !buildN {
		if err := javac.Run(); err != nil {
			buf.WriteTo(xout)
			return err
		}
	}

	if buildX {
		printcmd("jar c -C %s .", dst)
	}
	if buildN {
		return nil
	}

	jarw := zip.NewWriter(w)
	jarwcreate := func(name string) (io.Writer, error) {
		if buildV {
			fmt.Fprintf(os.Stderr, "jar: %s\n", name)
		}
		return jarw.Create(name)
	}
	f, err := jarwcreate("META-INF/MANIFEST.MF")
	if err != nil {
		return err
	}
	fmt.Fprintf(f, manifestHeader)

	err = filepath.Walk(dst, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		if info.IsDir() {
			return nil
		}
		out, err := jarwcreate(filepath.ToSlash(path[len(dst)+1:]))
		if err != nil {
			return err
		}
		in, err := os.Open(path)
		if err != nil {
			return err
		}
		defer in.Close()
		_, err = io.Copy(out, in)
		return err
	})
	if err != nil {
		return err
	}
	return jarw.Close()
}

// androidAPIPath returns an android SDK platform directory under ANDROID_HOME.
// If there are multiple platforms that satisfy the minimum version requirement
// androidAPIPath returns the latest one among them.
func androidAPIPath() (string, error) {
	sdk := os.Getenv("ANDROID_HOME")
	if sdk == "" {
		return "", fmt.Errorf("ANDROID_HOME environment var is not set")
	}
	sdkDir, err := os.Open(filepath.Join(sdk, "platforms"))
	if err != nil {
		return "", fmt.Errorf("failed to find android SDK platform: %v", err)
	}
	defer sdkDir.Close()
	fis, err := sdkDir.Readdir(-1)
	if err != nil {
		return "", fmt.Errorf("failed to find android SDK platform (min API level: %d): %v", minAndroidAPI, err)
	}

	var apiPath string
	var apiVer int
	for _, fi := range fis {
		name := fi.Name()
		if !fi.IsDir() || !strings.HasPrefix(name, "android-") {
			continue
		}
		n, err := strconv.Atoi(name[len("android-"):])
		if err != nil || n < minAndroidAPI {
			continue
		}
		p := filepath.Join(sdkDir.Name(), name)
		_, err = os.Stat(filepath.Join(p, "android.jar"))
		if err == nil && apiVer < n {
			apiPath = p
			apiVer = n
		}
	}
	if apiVer == 0 {
		return "", fmt.Errorf("failed to find android SDK platform (min API level: %d) in %s",
			minAndroidAPI, sdkDir.Name())
	}
	return apiPath, nil
}