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
基于Yoram Cohen的回答,这里有一个支持非静态目标目录的版本。
使用copyFileOrDir(getDataDir(), "")来写入应用程序内部存储文件夹/data/data/pkg_name/
Supports subfolders. Supports custom and non-static target directory Avoids copying "images" etc fake asset folders like private void copyFileOrDir(String TARGET_BASE_PATH, String path) { AssetManager assetManager = this.getAssets(); String assets[] = null; try { Log.i("tag", "copyFileOrDir() "+path); assets = assetManager.list(path); if (assets.length == 0) { copyFile(TARGET_BASE_PATH, path); } else { String fullPath = TARGET_BASE_PATH + "/" + path; Log.i("tag", "path="+fullPath); File dir = new File(fullPath); if (!dir.exists() && !path.startsWith("images") && !path.startsWith("sounds") && !path.startsWith("webkit")) if (!dir.mkdirs()) Log.i("tag", "could not create dir "+fullPath); for (int i = 0; i < assets.length; ++i) { String p; if (path.equals("")) p = ""; else p = path + "/"; if (!path.startsWith("images") && !path.startsWith("sounds") && !path.startsWith("webkit")) copyFileOrDir(TARGET_BASE_PATH, p + assets[i]); } } } catch (IOException ex) { Log.e("tag", "I/O Exception", ex); } } private void copyFile(String TARGET_BASE_PATH, String filename) { AssetManager assetManager = this.getAssets(); InputStream in = null; OutputStream out = null; String newFileName = null; try { Log.i("tag", "copyFile() "+filename); in = assetManager.open(filename); if (filename.endsWith(".jpg")) // extension was added to avoid compression on APK file newFileName = TARGET_BASE_PATH + "/" + filename.substring(0, filename.length()-4); else newFileName = TARGET_BASE_PATH + "/" + 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", "Exception in copyFile() of "+newFileName); Log.e("tag", "Exception in copyFile() "+e.toString()); } }
其他回答
基于您的解决方案,我自己做了一些事情来允许子文件夹。有些人可能会觉得这很有用:
...
copyFileOrDir("myrootdir");
...
private void copyFileOrDir(String path) {
AssetManager assetManager = this.getAssets();
String assets[] = null;
try {
assets = assetManager.list(path);
if (assets.length == 0) {
copyFile(path);
} else {
String fullPath = "/data/data/" + this.getPackageName() + "/" + path;
File dir = new File(fullPath);
if (!dir.exists())
dir.mkdir();
for (int i = 0; i < assets.length; ++i) {
copyFileOrDir(path + "/" + assets[i]);
}
}
} catch (IOException ex) {
Log.e("tag", "I/O Exception", ex);
}
}
private void copyFile(String filename) {
AssetManager assetManager = this.getAssets();
InputStream in = null;
OutputStream out = null;
try {
in = assetManager.open(filename);
String newFileName = "/data/data/" + this.getPackageName() + "/" + 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());
}
}
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();
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"
}
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。
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"))
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