你可以用Kotlin在几个步骤中做到这一点，在这里我只复制几个文件，而不是所有从资产到我的应用程序文件目录。

private fun copyRelatedAssets() {
    val assets = arrayOf("myhome.html", "support.css", "myscript.js", "style.css")
    assets.forEach {
        val inputStream = requireContext().assets.open(it)
        val nameSplit = it.split(".")
        val name = nameSplit[0]
        val extension = nameSplit[1]
        val path = inputStream.getFilePath(requireContext().filesDir, name, extension)
        Log.v(TAG, path)
    }
}

这是扩展函数，

fun InputStream.getFilePath(dir: File, name: String, extension: String): String {
    val file = File(dir, "$name.$extension")
    val outputStream = FileOutputStream(file)
    this.copyTo(outputStream, 4096)
    return file.absolutePath
}

洛格猫

/data/user/0/com.***.***/files/myhome.html
/data/user/0/com.***.***/files/support.css
/data/user/0/com.***.***/files/myscript.js
/data/user/0/com.***.***/files/style.css

复制所有文件和目录从资产到您的文件夹!

为了更好地复制，使用apache Commons IO

public void doCopyAssets() throws IOException {
    File externalFilesDir = context.getExternalFilesDir(null);

    doCopy("", externalFilesDir.getPath());

}

//这是复制的主要方法

private void doCopy(String dirName, String outPath) throws IOException {

    String[] srcFiles = assets.list(dirName);//for directory
    for (String srcFileName : srcFiles) {
        String outFileName = outPath + File.separator + srcFileName;
        String inFileName = dirName + File.separator + srcFileName;
        if (dirName.equals("")) {// for first time
            inFileName = srcFileName;
        }
        try {
            InputStream inputStream = assets.open(inFileName);
            copyAndClose(inputStream, new FileOutputStream(outFileName));
        } catch (IOException e) {//if directory fails exception
            new File(outFileName).mkdir();
            doCopy(inFileName, outFileName);
        }

    }
}

public static void closeQuietly(AutoCloseable autoCloseable) {
    try {
        if(autoCloseable != null) {
            autoCloseable.close();
        }
    } catch(IOException ioe) {
        //skip
    }
}

public static void copyAndClose(InputStream input, OutputStream output) throws IOException {
    copy(input, output);
    closeQuietly(input);
    closeQuietly(output);
}

public static void copy(InputStream input, OutputStream output) throws IOException {
    byte[] buffer = new byte[1024];
    int n = 0;
    while(-1 != (n = input.read(buffer))) {
        output.write(buffer, 0, n);
    }
}

这在Kotlin中是一种简洁的方式。

    fun AssetManager.copyRecursively(assetPath: String, targetFile: File) {
        val list = list(assetPath)
        if (list.isEmpty()) { // assetPath is file
            open(assetPath).use { input ->
                FileOutputStream(targetFile.absolutePath).use { output ->
                    input.copyTo(output)
                    output.flush()
                }
            }

        } else { // assetPath is folder
            targetFile.delete()
            targetFile.mkdir()

            list.forEach {
                copyRecursively("$assetPath/$it", File(targetFile, it))
            }
        }
    }

对于正在更新到Kotlin的用户:

按照以下步骤避免FileUriExposedExceptions， 假设用户已授予WRITE_EXTERNAL_STORAGE权限，并且您的文件位于assets/pdfs/mypdf.pdf。

private fun openFile() {
    var inputStream: InputStream? = null
    var outputStream: OutputStream? = null
    try {
        val file = File("${activity.getExternalFilesDir(null)}/$PDF_FILE_NAME")
        if (!file.exists()) {
            inputStream = activity.assets.open("$PDF_ASSETS_PATH/$PDF_FILE_NAME")
            outputStream = FileOutputStream(file)
            copyFile(inputStream, outputStream)
        }

        val uri = FileProvider.getUriForFile(
            activity,
            "${BuildConfig.APPLICATION_ID}.provider.GenericFileProvider",
            file
        )
        val intent = Intent(Intent.ACTION_VIEW).apply {
            setDataAndType(uri, "application/pdf")
            addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
            addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY)
        }
        activity.startActivity(intent)
    } catch (ex: IOException) {
        ex.printStackTrace()
    } catch (ex: ActivityNotFoundException) {
        ex.printStackTrace()
    } finally {
        inputStream?.close()
        outputStream?.flush()
        outputStream?.close()
    }
}

@Throws(IOException::class)
private fun copyFile(input: InputStream, output: OutputStream) {
    val buffer = ByteArray(1024)
    var read: Int = input.read(buffer)
    while (read != -1) {
        output.write(buffer, 0, read)
        read = input.read(buffer)
    }
}

companion object {
    private const val PDF_ASSETS_PATH = "pdfs"
    private const val PDF_FILE_NAME = "mypdf.pdf"
}

在Kotlin中，这可以用一行完成!

为InputStream添加扩展乐趣

fun InputStream.toFile(to: File){
    this.use { input->
        to.outputStream().use { out->
            input.copyTo(out)
        }
    }
}

然后使用它

MainActivity.kt

assets.open("test.zip").toFile(File(filesDir,"test.zip"))

这里是一个针对当前Android设备的清理版本，功能方法设计，以便您可以将其复制到AssetsHelper类，例如;)

/**
 * 
 * Info: prior to Android 2.3, any compressed asset file with an
 * uncompressed size of over 1 MB cannot be read from the APK. So this
 * should only be used if the device has android 2.3 or later running!
 * 
 * @param c
 * @param targetFolder
 *            e.g. {@link Environment#getExternalStorageDirectory()}
 * @throws Exception
 */
@TargetApi(Build.VERSION_CODES.GINGERBREAD)
public static boolean copyAssets(AssetManager assetManager,
        File targetFolder) throws Exception {
    Log.i(LOG_TAG, "Copying files from assets to folder " + targetFolder);
    return copyAssets(assetManager, "", targetFolder);
}

/**
 * The files will be copied at the location targetFolder+path so if you
 * enter path="abc" and targetfolder="sdcard" the files will be located in
 * "sdcard/abc"
 * 
 * @param assetManager
 * @param path
 * @param targetFolder
 * @return
 * @throws Exception
 */
public static boolean copyAssets(AssetManager assetManager, String path,
        File targetFolder) throws Exception {
    Log.i(LOG_TAG, "Copying " + path + " to " + targetFolder);
    String sources[] = assetManager.list(path);
    if (sources.length == 0) { // its not a folder, so its a file:
        copyAssetFileToFolder(assetManager, path, targetFolder);
    } else { // its a folder:
        if (path.startsWith("images") || path.startsWith("sounds")
                || path.startsWith("webkit")) {
            Log.i(LOG_TAG, "  > Skipping " + path);
            return false;
        }
        File targetDir = new File(targetFolder, path);
        targetDir.mkdirs();
        for (String source : sources) {
            String fullSourcePath = path.equals("") ? source : (path
                    + File.separator + source);
            copyAssets(assetManager, fullSourcePath, targetFolder);
        }
    }
    return true;
}

private static void copyAssetFileToFolder(AssetManager assetManager,
        String fullAssetPath, File targetBasePath) throws IOException {
    InputStream in = assetManager.open(fullAssetPath);
    OutputStream out = new FileOutputStream(new File(targetBasePath,
            fullAssetPath));
    byte[] buffer = new byte[16 * 1024];
    int read;
    while ((read = in.read(buffer)) != -1) {
        out.write(buffer, 0, read);
    }
    in.close();
    out.flush();
    out.close();
}