How to copy files from 'assets' folder to

2楼-- · 2018-12-31 02:12

Copy all files and directories from assets to your folder!

for copying better use apache commons io

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

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

}

//THIS IS MAIN METHOD FOR COPY

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);
    }
}

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君临天下

3楼-- · 2018-12-31 02:13

There are essentially two ways to do this.

First, you can use AssetManager.open and, as described by Rohith Nandakumar and iterate over the inputstream.

Second, you can use AssetManager.openFd, which allows you to use a FileChannel (which has the [transferTo](https://developer.android.com/reference/java/nio/channels/FileChannel.html#transferTo(long, long, java.nio.channels.WritableByteChannel)) and [transferFrom](https://developer.android.com/reference/java/nio/channels/FileChannel.html#transferFrom(java.nio.channels.ReadableByteChannel, long, long)) methods), so you don't have to loop over the input stream yourself.

I will describe the openFd method here.

Compression

First you need to ensure that the file is stored uncompressed. The packaging system may choose to compress any file with an extension that is not marked as noCompress, and compressed files cannot be memory mapped, so you will have to rely on AssetManager.open in that case.

You can add a '.mp3' extension to your file to stop it from being compressed, but the proper solution is to modify your app/build.gradle file and add the following lines (to disable compression of PDF files)

aaptOptions {
    noCompress 'pdf'
}

File packing

Note that the packager can still pack multiple files into one, so you can't just read the whole file the AssetManager gives you. You need to to ask the AssetFileDescriptor which parts you need.

Finding the correct part of the packed file

Once you've ensured your file is stored uncompressed, you can use the AssetManager.openFd method to obtain an AssetFileDescriptor, which can be used to obtain a FileInputStream (unlike AssetManager.open, which returns an InputStream) that contains a FileChannel. It also contains the starting offset (getStartOffset) and size (getLength), which you need to obtain the correct part of the file.

Implementation

An example implementation is given below:

private void copyFileFromAssets(String in_filename, File out_file){
    Log.d("copyFileFromAssets", "Copying file '"+in_filename+"' to '"+out_file.toString()+"'");
    AssetManager assetManager = getApplicationContext().getAssets();
    FileChannel in_chan = null, out_chan = null;
    try {
        AssetFileDescriptor in_afd = assetManager.openFd(in_filename);
        FileInputStream in_stream = in_afd.createInputStream();
        in_chan = in_stream.getChannel();
        Log.d("copyFileFromAssets", "Asset space in file: start = "+in_afd.getStartOffset()+", length = "+in_afd.getLength());
        FileOutputStream out_stream = new FileOutputStream(out_file);
        out_chan = out_stream.getChannel();
        in_chan.transferTo(in_afd.getStartOffset(), in_afd.getLength(), out_chan);
    } catch (IOException ioe){
        Log.w("copyFileFromAssets", "Failed to copy file '"+in_filename+"' to external storage:"+ioe.toString());
    } finally {
        try {
            if (in_chan != null) {
                in_chan.close();
            }
            if (out_chan != null) {
                out_chan.close();
            }
        } catch (IOException ioe){}
    }
}

This answer is based on JPM's answer.

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千与千寻千般痛.

4楼-- · 2018-12-31 02:14

I know this has been answered but I have a slightly more elegant way to copy from asset directory to a file on the sdcard. It requires no "for" loop but instead uses File Streams and Channels to do the work.

(Note) If using any type of compressed file, APK, PDF, ... you may want to rename the file extension before inserting into asset and then rename once you copy it to 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();
}

A way to copy a file without having to loop through it.

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();
    }
}

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谁念西风独自凉

5楼-- · 2018-12-31 02:14

Here is a cleaned up version for current Android devices, functional method design so that you can copy it to an AssetsHelper class e.g ;)

/**
 * 
 * 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();
}

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步步皆殇っ

6楼-- · 2018-12-31 02:16

Based on Yoram Cohen answer, here is a version that supports non static target directory.

Invoque with copyFileOrDir(getDataDir(), "") to write to internal app storage folder /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());
}

}

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美炸的是我

7楼-- · 2018-12-31 02:20

This is by far the best solution I have been able to find on the internet. I've used the following link https://gist.github.com/mhasby/026f02b33fcc4207b302a60645f6e217,
but it had a single error which I fixed and then it works like a charm. Here's my code. You can easily use it as it is an independent java class.

public class CopyAssets {
public static void copyAssets(Context context) {
    AssetManager assetManager = context.getAssets();
    String[] files = null;
    try {
        files = assetManager.list("");
    } 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(filename);

            out = new FileOutputStream(Environment.getExternalStorageDirectory()+"/www/resources/" + filename);
            copyFile(in, out);
        } catch(IOException e) {
            Log.e("tag", "Failed to copy asset file: " + filename, e);
        }
        finally {
            if (in != null) {
                try {
                    in.close();
                    in = null;
                } catch (IOException e) {

                }
            }
            if (out != null) {
                try {
                    out.flush();
                    out.close();
                    out = null;
                } catch (IOException e) {

                }
            }
        }
    }
}

public static 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);
    }
}}

As you can see, just create an instance of CopyAssets in your java class which has an activity. Now this part is important, as far as my testing and researching on the internet, You cannot use AssetManager if the class has no activity . It has something to do with the context of the java class.
Now, the c.copyAssets(getApplicationContext()) is an easy way to access the method, where c is and instance of CopyAssets class. As per my requirement, I allowed the program to copy all my resource files inside the asset folder to the /www/resources/ of my internal directory.
You can easily find out the part where you need to make changes to the directory as per your use. Feel free to ping me if you need any help.

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