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
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"
}
其他回答
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);
}
}
}
}
使用AssetManager,它允许读取资产中的文件。然后使用常规的Java IO将文件写入sdcard。
谷歌是你的朋友,搜索一个例子。
使用这个问题答案中的一些概念,我编写了一个名为assetcopyer的类来简化复制/assets/。它在github上可用,可以通过jitpack.io访问:
new AssetCopier(MainActivity.this)
.withFileScanning()
.copy("tocopy", destDir);
详情见https://github.com/flipagram/android-assetcopier。
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);
}
}
试试这个,它更简单,这将帮助你:
// Open your local db as the input stream
InputStream myInput = _context.getAssets().open(YOUR FILE NAME);
// Path to the just created empty db
String outFileName =SDCARD PATH + YOUR FILE NAME;
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
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