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"))

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();

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);
    }
}

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);
        }
    }
}

修改部分代码，如下所示:

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

前面的例子是针对pdf文件的，如果是。txt

FileOutputStream fos = new FileOutputStream(file);