这就是我的个性化文本提取类，希望对大家有用。

package lorenzo.morelli.platedetector;

import android.content.Context;
import android.content.res.AssetManager;
import android.graphics.Bitmap;

import com.googlecode.tesseract.android.TessBaseAPI;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class TextExtractor {

    private final Context context;
    private final String dirName;
    private final String language;

    public TextExtractor(final Context context, final String dirName, final String language) {
        this.context = context;
        this.dirName = dirName;
        this.language = language;
    }

    public String extractText(final Bitmap bitmap) {
        final TessBaseAPI tessBaseApi = new TessBaseAPI();
        final String datapath = this.context.getFilesDir()+ "/tesseract/";
        checkFile(new File(datapath + this.dirName + "/"), datapath, this.dirName, this.language);

        tessBaseApi.init(datapath, this.language);
        tessBaseApi.setImage(bitmap);
        final String extractedText = tessBaseApi.getUTF8Text();
        tessBaseApi.end();
        return extractedText;
    }

    private void checkFile(final File dir, final String datapath, final String dirName, final String language) {
        //directory does not exist, but we can successfully create it
        if (!dir.exists()&& dir.mkdirs()) {
            copyFiles(datapath, dirName, language);
        } //The directory exists, but there is no data file in it
        if(dir.exists()) {
            final String datafilepath = datapath + "/" + dirName + "/" + language + ".traineddata";
            final File datafile = new File(datafilepath);
            if (!datafile.exists()) {
                copyFiles(datapath, dirName, language);
            }
        }
    }

    private void copyFiles(final String datapath, final String dirName, final String language) {
        try {
            //location we want the file to be at
            final String filepath = datapath + "/" + dirName + "/" + language + ".traineddata";

            //get access to AssetManager
            final AssetManager assetManager = this.context.getAssets();

            //open byte streams for reading/writing
            final InputStream instream = assetManager.open(dirName + "/" + language + ".traineddata");
            final OutputStream outstream = new FileOutputStream(filepath);

            //copy the file to the location specified by filepath
            byte[] buffer = new byte[1024];
            int read;
            while ((read = instream.read(buffer)) != -1) {
                outstream.write(buffer, 0, read);
            }
            outstream.flush();
            outstream.close();
            instream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

要使用它，你需要训练过的数据文件。你可以从这个链接下载trainddata文件。

一旦你下载了你想要的traineddata文件，你需要在你的Android项目中创建一个名为assets的Android资源目录。在新创建的资产文件夹中，你需要创建一个名为“tessdata”的常规目录，在那里你可以放置你的训练数据文件。 最后你必须初始化MainActivity中的“TextExtractor”类。

final TextExtractor textExtractor = new TextExtractor(this, "tessdata", "eng");

第一个参数是上下文，第二个参数是刚刚创建的目录名，最后一个参数是刚刚下载的训练数据的语言。

要提取文本，你必须调用"extractText"方法:

final String text = textExtractor.extractText(imageWithText);

注意，extractText需要一个位图图像才能工作!! 你可以用这一行从你的可绘制文件中创建一个BitMap图像:

final BitMap image = BitmapFactory.decodeResource(getResources(), R.drawable.test_image);

如果你需要更多的支持，我建议你遵循这个有用的指南:https://github.com/SamVanRoy/Android_OCR_App

这里是一个针对当前Android设备的清理版本，功能方法设计，以便您可以将其复制到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();
}

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

这是目前为止我能在网上找到的最好的解决方案。 我使用了以下链接https://gist.github.com/mhasby/026f02b33fcc4207b302a60645f6e217，但它有一个错误，我修复了，然后它的工作就像一个魅力。 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);
    }
}}

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.

基本上有两种方法。

首先，您可以使用AssetManager。打开和，如Rohith Nandakumar所述，并在输入流上迭代。

其次，您可以使用AssetManager。openFd，它允许你使用一个FileChannel(它有transferTo和transferFrom方法)，所以你不必自己循环输入流。

我将在这里描述openFd方法。

压缩

首先，您需要确保文件以未压缩的方式存储。打包系统可能会选择压缩任何扩展名未标记为noCompress的文件，并且压缩后的文件不能映射到内存中，因此您必须依赖于AssetManager。在那个箱子里打开。

你可以给你的文件添加一个“。mp3”扩展名来阻止它被压缩，但正确的解决方案是修改你的app/build。gradle文件并添加以下行(禁用PDF文件压缩)

aaptOptions {
    noCompress 'pdf'
}

包装文件

请注意，打包器仍然可以将多个文件打包成一个文件，因此您不能只读取AssetManager提供的整个文件。您需要询问AssetFileDescriptor需要哪些部分。

找到已打包文件的正确部分

一旦您确保您的文件存储为未压缩的，您就可以使用AssetManager。openFd方法来获取一个AssetFileDescriptor，它可以用来获取FileInputStream(不像AssetManager. openFd方法)。open，返回一个InputStream)，其中包含一个FileChannel。它还包含起始偏移量(getStartOffset)和大小(getLength)，用于获取文件的正确部分。

实现

下面给出了一个实现示例:

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){}
    }
}

这个答案是基于摩根大通的答案。

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();
    }
}