我在资产文件夹里有几个文件。我需要把它们都复制到一个文件夹,比如/sdcard/folder。我想从一个线程中做这件事。我该怎么做?
当前回答
您还可以使用Guava的ByteStream将文件从资产文件夹复制到SD卡。这是我最终得到的解决方案,将文件递归地从资产文件夹复制到SD卡:
/**
* Copies all assets in an assets directory to the SD file system.
*/
public class CopyAssetsToSDHelper {
public static void copyAssets(String assetDir, String targetDir, Context context)
throws IOException {
AssetManager assets = context.getAssets();
String[] list = assets.list(assetDir);
for (String f : Objects.requireNonNull(list)) {
if (f.indexOf(".") > 1) { // check, if this is a file
File outFile = new File(context.getExternalFilesDir(null),
String.format("%s/%s", targetDir, f));
File parentFile = outFile.getParentFile();
if (!Objects.requireNonNull(parentFile).exists()) {
if (!parentFile.mkdirs()) {
throw new IOException(String.format("Could not create directory %s.",
parentFile));
}
}
try (InputStream fin = assets.open(String.format("%s/%s", assetDir, f));
OutputStream fout = new FileOutputStream(outFile)) {
ByteStreams.copy(fin, fout);
}
} else { // This is a directory
copyAssets(String.format("%s/%s", assetDir, f), String.format("%s/%s", targetDir, f),
context);
}
}
}
}
其他回答
轻微修改以上回答复制文件夹递归和适应自定义目的地。
public void copyFileOrDir(String path, String destinationDir) {
AssetManager assetManager = this.getAssets();
String assets[] = null;
try {
assets = assetManager.list(path);
if (assets.length == 0) {
copyFile(path,destinationDir);
} else {
String fullPath = destinationDir + "/" + path;
File dir = new File(fullPath);
if (!dir.exists())
dir.mkdir();
for (int i = 0; i < assets.length; ++i) {
copyFileOrDir(path + "/" + assets[i], destinationDir + path + "/" + assets[i]);
}
}
} catch (IOException ex) {
Log.e("tag", "I/O Exception", ex);
}
}
private void copyFile(String filename, String destinationDir) {
AssetManager assetManager = this.getAssets();
String newFileName = destinationDir + "/" + filename;
InputStream in = null;
OutputStream out = null;
try {
in = assetManager.open(filename);
out = new FileOutputStream(newFileName);
byte[] buffer = new byte[1024];
int read;
while ((read = in.read(buffer)) != -1) {
out.write(buffer, 0, read);
}
in.close();
in = null;
out.flush();
out.close();
out = null;
} catch (Exception e) {
Log.e("tag", e.getMessage());
}
new File(newFileName).setExecutable(true, false);
}
修改了@ danya的SO回答
private void copyAssets(String path, String outPath) {
AssetManager assetManager = this.getAssets();
String assets[];
try {
assets = assetManager.list(path);
if (assets.length == 0) {
copyFile(path, outPath);
} else {
String fullPath = outPath + "/" + path;
File dir = new File(fullPath);
if (!dir.exists())
if (!dir.mkdir()) Log.e(TAG, "No create external directory: " + dir );
for (String asset : assets) {
copyAssets(path + "/" + asset, outPath);
}
}
} catch (IOException ex) {
Log.e(TAG, "I/O Exception", ex);
}
}
private void copyFile(String filename, String outPath) {
AssetManager assetManager = this.getAssets();
InputStream in;
OutputStream out;
try {
in = assetManager.open(filename);
String newFileName = outPath + "/" + filename;
out = new FileOutputStream(newFileName);
byte[] buffer = new byte[1024];
int read;
while ((read = in.read(buffer)) != -1) {
out.write(buffer, 0, read);
}
in.close();
out.flush();
out.close();
} catch (Exception e) {
Log.e(TAG, e.getMessage());
}
}
准备工作
在src /主/资产 添加名称折叠文件夹
使用
File outDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).toString());
copyAssets("fold",outDir.toString());
在外部目录中找到折叠资产内的所有文件和目录
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"
}
我知道这已经回答,但我有一个稍微更优雅的方式从资产目录复制到sdcard上的文件。它不需要“for”循环,而是使用文件流和通道来完成工作。
(注)如果使用任何类型的压缩文件,APK, PDF,…你可能想重命名文件扩展名之前插入到资产,然后重命名一旦你复制到SDcard)
AssetManager am = context.getAssets();
AssetFileDescriptor afd = null;
try {
afd = am.openFd( "MyFile.dat");
// Create new file to copy into.
File file = new File(Environment.getExternalStorageDirectory() + java.io.File.separator + "NewFile.dat");
file.createNewFile();
copyFdToFile(afd.getFileDescriptor(), file);
} catch (IOException e) {
e.printStackTrace();
}
一种复制文件而不必循环遍历它的方法。
public static void copyFdToFile(FileDescriptor src, File dst) throws IOException {
FileChannel inChannel = new FileInputStream(src).getChannel();
FileChannel outChannel = new FileOutputStream(dst).getChannel();
try {
inChannel.transferTo(0, inChannel.size(), outChannel);
} finally {
if (inChannel != null)
inChannel.close();
if (outChannel != null)
outChannel.close();
}
}
基于Rohith Nandakumar的解决方案,我自己做了一些事情,从资产的子文件夹中复制文件。“资产/ MyFolder”)。此外,在尝试再次复制之前,我正在检查文件是否已经存在于sdcard中。
private void copyAssets() {
AssetManager assetManager = getAssets();
String[] files = null;
try {
files = assetManager.list("MyFolder");
} catch (IOException e) {
Log.e("tag", "Failed to get asset file list.", e);
}
if (files != null) for (String filename : files) {
InputStream in = null;
OutputStream out = null;
try {
in = assetManager.open("MyFolder/"+filename);
File outFile = new File(getExternalFilesDir(null), filename);
if (!(outFile.exists())) {// File does not exist...
out = new FileOutputStream(outFile);
copyFile(in, out);
}
} catch(IOException e) {
Log.e("tag", "Failed to copy asset file: " + filename, e);
}
finally {
if (in != null) {
try {
in.close();
} catch (IOException e) {
// NOOP
}
}
if (out != null) {
try {
out.close();
} catch (IOException e) {
// NOOP
}
}
}
}
}
private void copyFile(InputStream in, OutputStream out) throws IOException {
byte[] buffer = new byte[1024];
int read;
while((read = in.read(buffer)) != -1){
out.write(buffer, 0, read);
}
}
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