如何将文件从“资产”文件夹复制到sdcard?


251

我的文件assets夹中有几个文件。我需要将所有文件都复制到一个文件夹/ sdcard / folder。我想从一个线程中做到这一点。我该怎么做?



2
在复制/粘贴以下(一种极好的!)解决方案之一之前,请考虑使用此库在一行代码中完成该任务:stackoverflow.com/a/41970539/9648
JohnnyLambada

Answers:


346

如果有人遇到同样的问题,这就是我的做法

private void copyAssets() {
    AssetManager assetManager = 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);
          File outFile = new File(getExternalFilesDir(null), filename);
          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);
    }
}

参考:使用Java移动文件


28
要在sdcard中写入文件,您必须在清单上授予权限,例如<uses-permission android:name =“ android.permission.WRITE_EXTERNAL_STORAGE” />
IronBlossom 2012年

22
我也不会依靠SD卡正在位于/ SD卡,但检索与Environment.getExternalStorageDirectory()的路径
Axarydax

2
我应该使用:16 * 1024(16kb)我倾向于选择16K或32K,以在内存使用和性能之间取得良好的平衡。
南武

3
@rciovati收到此运行时错误Failed to copy asset file: myfile.txt java.io.FileNotFoundException: myfile.txt at android.content.res.AssetManager.openAsset(Native Method)
likejudo

7
对我来说,此代码仅在添加以下代码后起作用:in = assetManager.open("images-wall/"+filename);其中“ images-wall”是我在资产中的文件夹
Ultimo_m 2014年

62

根据您的解决方案,我做了自己的事情来允许子文件夹。有人会发现这很有帮助:

...

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());
    }

}

1
assetManager.list(path)可能在设备上运行缓慢,因此无法事先创建目录路径以使用assetsdir:find . -name "*" -type f -exec ls -l {} \; | awk '{print substr($9,3)}' >> assets.list
alexkasko 2013年

3
不错的解决方案!唯一需要解决的方法是在copyFileOrDir()的开头修剪前导分隔符:path = path.startsWith(“ /”)?path.substring(1):路径;
Cross_ 2014年

此stackoverflow在某些设备上,例如:S5
相信


1
...并在finally块中关闭流))
Mixaz's

48

由于某些错误,以上解决方案无法正常工作:

  • 目录创建不起作用
  • Android返回的资产还包含三个文件夹:图像,声音和Webkit
  • 添加了处理大文件的方法:将扩展名.mp3添加到项目中Assets文件夹中的文件中,并且在复制过程中,目标文件将不具有.mp3扩展名

这是代码(我离开了Log语句,但是现在可以删除它们):

final static String TARGET_BASE_PATH = "/sdcard/appname/voices/";

private void copyFilesToSdCard() {
    copyFileOrDir(""); // copy all files in assets folder in my project
}

private void copyFileOrDir(String path) {
    AssetManager assetManager = this.getAssets();
    String assets[] = null;
    try {
        Log.i("tag", "copyFileOrDir() "+path);
        assets = assetManager.list(path);
        if (assets.length == 0) {
            copyFile(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( p + 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;
    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());
    }

}

编辑:更正了一个错误放置的“;” 抛出系统的“无法创建目录”错误。


4
这必须成为解决方案!
Massimo Variolo 2013年

1
注意:Log.i(“ tag”,“无法创建目录” + fullPath); 总是像那样发生; 如果放错了位置。
RoundSparrow hilltx 2014年

太棒了!非常感谢!但是,为什么要检查jpg文件?
2015年

32

我知道已经解决了这个问题,但是我有一种更优雅的方法可以从资产目录复制到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。

(注意)如果使用任何类型的压缩文件,如APK,PDF,...,则可能需要先将文件扩展名重命名,然后再插入资产中,然后将其复制到SD卡后再重命名)

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();
}

一种无需循环即可复制文件的方法。

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();
    }
}

在其他解决方案上喜欢这个,有点整洁。我的轻微修改,包括创建丢失的fileFolders。干杯!
克里斯·詹金斯(Chris.Jenkins)2012年

3
对于我来说,This file can not be opened as a file descriptor; it is probably compressed这将无法通过文件描述符,而是pdf文件。知道如何解决?
ʀʀʏ2012年

1
假定inChannel.size()返回文件大小的大小。它没有这样的保证。我正在为2个文件(每个450 KiB)获得2.5 MiB。
AI0867

1
我刚刚发现AssetFileDescriptor.getLength()将返回正确的文件大小。
AI0867

1
除上述内容外,资产可能不会在文件描述符中的位置0开始。AssetFileDescriptor.getStartOffset()将返回起始偏移量。
AI0867

5

试试看,它要简单得多,这对您有帮助:

// 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();

5

在Kotlin中,这将是一种简洁的方式。

    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))
            }
        }
    }

list(assetPath)?. let {...}实际上。可以为空。
加博尔

4

这是当前Android设备的清理版本,具有功能性方法设计,因此您可以将其复制到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();
}

4

修改该SO通过@DannyA答案

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

src/main/assets 具有名称的添加文件夹中fold

用法

File outDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS).toString());
copyAssets("fold",outDir.toString());

在外部目录中,找到折叠资产中的所有文件和目录


3

将资产中的所有文件和目录复制到您的文件夹中!

用于更好地复制apache commons io

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

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

}

//这是主要的复印方法

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);
    }
}

2

根据Yoram Cohen的回答,这是一个支持非静态目标目录的版本。

发票copyFileOrDir(getDataDir(), "")以写入内部应用程序存储文件夹/ data / data / pkg_name /

  • 支持子文件夹。
  • 支持自定义和非静态目标目录
  • 避免复制“图像”等假资产文件夹,例如

    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());
    }
    
    }


2

基本上有两种方法可以做到这一点。

首先,您可以使用AssetManager.open并按照Rohith Nandakumar的描述进行操作,并遍历输入流。

其次,您可以使用AssetManager.openFd,它允许您使用FileChannel (具有[transferTo](https://developer.android.com/reference/java/nio/channels/FileChannel.html#transferTo ( long, long,java.nio.channels.WritableByteChannel))和[transferFrom](https://developer.android.com/reference/java/nio/channels/FileChannel.html#transferFrom (java.nio.channels.ReadableByteChannel ,long, long))方法),因此您不必自己遍历输入流。

我将在这里描述openFd方法。

压缩

首先,您需要确保文件未压缩存储。打包系统可以选择压缩任何扩展名未标记为noCompress的文件,并且压缩后的文件无法进行内存映射,因此在这种情况下,您将不得不依靠AssetManager.open

您可以在文件中添加扩展名“ .mp3”以阻止其压缩,但是正确的解决方案是修改app / build.gradle文件并添加以下几行(以禁用PDF文件的压缩)

aaptOptions {
    noCompress 'pdf'
}

文件包装

请注意,打包程序仍然可以将多个文件打包为一个文件,因此您不能只读取AssetManager为您提供的整个文件。您需要询问AssetFileDescriptor您需要哪些部分。

找到打包文件的正确部分

确保文件未压缩存储后,就可以使用AssetManager.openFd方法获取AssetFileDescriptor,后者可以用于获取包含FileChannelFileInputStream(与AssetManager.open不同,后者返回InputStream)。它还包含起始偏移量(getStartOffset)大小(getLength),您需要获取它们的正确位置。

实作

下面给出一个示例实现:

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){}
    }
}

该答案基于JPM的答案


1
import android.app.Activity;
import android.content.Intent;
import android.content.res.AssetManager;
import android.net.Uri;
import android.os.Environment;
import android.os.Bundle;
import android.util.Log;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;


public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        copyReadAssets();
    }


    private void copyReadAssets()
    {
        AssetManager assetManager = getAssets();

        InputStream in = null;
        OutputStream out = null;

        String strDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS)+ File.separator + "Pdfs";
        File fileDir = new File(strDir);
        fileDir.mkdirs();   // crear la ruta si no existe
        File file = new File(fileDir, "example2.pdf");



        try
        {

            in = assetManager.open("example.pdf");  //leer el archivo de assets
            out = new BufferedOutputStream(new FileOutputStream(file)); //crear el archivo


            copyFile(in, out);
            in.close();
            in = null;
            out.flush();
            out.close();
            out = null;
        } catch (Exception e)
        {
            Log.e("tag", e.getMessage());
        }

        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.setDataAndType(Uri.parse("file://" + Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS) + File.separator + "Pdfs" + "/example2.pdf"), "application/pdf");
        startActivity(intent);
    }

    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);
        }
    }
}

更改部分代码,如下所示:

out = new BufferedOutputStream(new FileOutputStream(file));

之前的示例适用于Pdfs,如果使用示例.txt

FileOutputStream fos = new FileOutputStream(file);

1

使用AssetManager,它允许读取资产中的文件。然后使用常规Java IO将文件写入sdcard。

Google是您的朋友,搜索示例。


1

嗨,大家好,我做了这样的事情。对于第N深度复制文件夹和文件进行复制。这允许您复制所有目录结构以从Android AssetManager复制:)

    private void manageAssetFolderToSDcard()
    {

        try
        {
            String arg_assetDir = getApplicationContext().getPackageName();
            String arg_destinationDir = FRConstants.ANDROID_DATA + arg_assetDir;
            File FolderInCache = new File(arg_destinationDir);
            if (!FolderInCache.exists())
            {
                copyDirorfileFromAssetManager(arg_assetDir, arg_destinationDir);
            }
        } catch (IOException e1)
        {

            e1.printStackTrace();
        }

    }


    public String copyDirorfileFromAssetManager(String arg_assetDir, String arg_destinationDir) throws IOException
    {
        File sd_path = Environment.getExternalStorageDirectory(); 
        String dest_dir_path = sd_path + addLeadingSlash(arg_destinationDir);
        File dest_dir = new File(dest_dir_path);

        createDir(dest_dir);

        AssetManager asset_manager = getApplicationContext().getAssets();
        String[] files = asset_manager.list(arg_assetDir);

        for (int i = 0; i < files.length; i++)
        {

            String abs_asset_file_path = addTrailingSlash(arg_assetDir) + files[i];
            String sub_files[] = asset_manager.list(abs_asset_file_path);

            if (sub_files.length == 0)
            {
                // It is a file
                String dest_file_path = addTrailingSlash(dest_dir_path) + files[i];
                copyAssetFile(abs_asset_file_path, dest_file_path);
            } else
            {
                // It is a sub directory
                copyDirorfileFromAssetManager(abs_asset_file_path, addTrailingSlash(arg_destinationDir) + files[i]);
            }
        }

        return dest_dir_path;
    }


    public void copyAssetFile(String assetFilePath, String destinationFilePath) throws IOException
    {
        InputStream in = getApplicationContext().getAssets().open(assetFilePath);
        OutputStream out = new FileOutputStream(destinationFilePath);

        byte[] buf = new byte[1024];
        int len;
        while ((len = in.read(buf)) > 0)
            out.write(buf, 0, len);
        in.close();
        out.close();
    }

    public String addTrailingSlash(String path)
    {
        if (path.charAt(path.length() - 1) != '/')
        {
            path += "/";
        }
        return path;
    }

    public String addLeadingSlash(String path)
    {
        if (path.charAt(0) != '/')
        {
            path = "/" + path;
        }
        return path;
    }

    public void createDir(File dir) throws IOException
    {
        if (dir.exists())
        {
            if (!dir.isDirectory())
            {
                throw new IOException("Can't create directory, a file is in the way");
            }
        } else
        {
            dir.mkdirs();
            if (!dir.isDirectory())
            {
                throw new IOException("Unable to create directory");
            }
        }
    }

最后创建一个Asynctask:

    private class ManageAssetFolders extends AsyncTask<Void, Void, Void>
    {

        @Override
        protected Void doInBackground(Void... arg0)
        {
            manageAssetFolderToSDcard();
            return null;
        }

    }

从您的活动中调用它:

    new ManageAssetFolders().execute();

1

略微修改以上答案即可递归复制文件夹并容纳自定义目标。

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);
}

1

基于Rohith Nandakumar的解决方案,我做了自己的事情来从资产的子文件夹(即“ assets / MyFolder ”)复制文件。另外,我正在尝试再次复制之前检查sdcard中是否已存在该文件。

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);
    }
}

0

这是迄今为止我在互联网上找到的最佳解决方案。我已经使用了以下链接https://gist.github.com/mhasby/026f02b33fcc4207b302a60645f6e217
但是它有一个错误,我已将其修复,然后像魅力一样工作。这是我的代码。您可以轻松使用它,因为它是一个独立的Java类。

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);
    }
}}

如您所见,只需CopyAssets在Java类中创建一个具有活动的实例。现在,对于我在Internet上的测试和研究而言,这部分很重要You cannot use AssetManager if the class has no activity。它与java类的上下文有关。
现在,这c.copyAssets(getApplicationContext())是一种访问方法,类的位置c和实例的简便方法CopyAssets。根据我的要求,我允许程序将文件asset夹中的所有资源文件复制到/www/resources/内部目录的。
您可以根据需要轻松找到需要更改目录的部分。如果您需要任何帮助,请随时与我联系。


0

对于那些要更新到Kotlin的人:

步骤,以避免FileUriExposedExceptions,假设用户已授予WRITE_EXTERNAL_STORAGE许可,并在文件中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"
}
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