Android Asset 资源文件拷贝

srcRelPath 为源文件相对于 assets 的相对路径，dstAbsPath 为目标文件的绝对路径。
当目标文件已经存在时，若 forceCopy 为 true，则覆盖；否则跳过。

import android.content.Context;
import android.content.res.AssetManager;
import android.util.Log;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;


public class AssetHelper {
    
    
    private static final String TAG = AssetHelper.class.getSimpleName();

    private AssetHelper() {
    
    
    }

    public static byte[] getAssetFileData(Context context, String fileName) {
    
    
        try (InputStream in = context.getResources().getAssets()
                .open(fileName, AssetManager.ACCESS_STREAMING)) {
    
    
            final int size = in.available();
            byte[] data = new byte[size];
            in.read(data, 0, size);
            return data;
        } catch (IOException e) {
    
    
            Log.e(TAG, "getAssetFileData: " + e);
            return null;
        }
    }

    public static boolean copyAssetFiles(Context context, String assetRelPath, String dstAbsPath,
            boolean forceCopy) {
    
    
        AssetManager assets = context.getResources().getAssets();
        return copyAssetFiles(assets, assetRelPath, dstAbsPath, forceCopy);
    }

    private static boolean copyAssetFiles(AssetManager assets, String srcRelPath, String dstAbsPath,
            boolean forceCopy) {
    
    
        String[] subFiles;
        try {
    
    
            subFiles = assets.list(srcRelPath);
        } catch (IOException e) {
    
    
            Log.e(TAG, "copyAssetFiles: " + e);
            return false;
        }
        if (subFiles.length == 0) {
    
    
            return copyAssetFile(assets, srcRelPath, dstAbsPath, forceCopy);
        } else {
    
    
            File dstDir = new File(dstAbsPath);
            if (!dstDir.isDirectory()) {
    
    
                if (!deleteFileOrDir(dstDir)) {
    
    
                    Log.e(TAG, "copyAssetFiles: Can not delete " + dstDir.getAbsolutePath());
                    return false;
                }
                if (!dstDir.mkdirs()) {
    
    
                    Log.e(TAG, "copyAssetFiles: Can not create " + dstDir.getAbsolutePath());
                    return false;
                }
            }
            boolean result = true;
            for (String subFile : subFiles) {
    
    
                result &= copyAssetFiles(assets, srcRelPath + File.separator + subFile,
                        dstAbsPath + File.separator + subFile, forceCopy);
            }
            return result;
        }
    }

    private static boolean copyAssetFile(AssetManager assets, String srcRelPath, String dstAbsPath,
            boolean forceCopy) {
    
    
        File file = new File(dstAbsPath);
        if (file.isFile() && !forceCopy) {
    
    
            return true;
        }
        if (!deleteFileOrDir(file)) {
    
    
            Log.e(TAG, "copyAssetFile: Can not delete " + file.getAbsolutePath());
            return false;
        }
        try (InputStream is = assets.open(srcRelPath, AssetManager.ACCESS_STREAMING);
             DataInputStream dis = new DataInputStream(is);
             FileOutputStream fos = new FileOutputStream(file);
             DataOutputStream dos = new DataOutputStream(fos);) {
    
    
            final int size = 1024;
            byte[] buffer = new byte[size];
            int len = 0;
            while ((len = dis.read(buffer, 0, size)) != -1) {
    
    
                dos.write(buffer, 0, len);
                dos.flush();
            }
            return true;
        } catch (IOException e) {
    
    
            Log.e(TAG, "copyAssetFile: " + e);
            return false;
        }
    }

    public static boolean deleteFileOrDir(File file) {
    
    
        if (!file.exists()) {
    
    
            return true;
        }
        if (file.isFile()) {
    
    
            return file.delete();
        }
        // file.isDirectory()
        File[] subFiles = file.listFiles();
        boolean subDeleted = true;
        if (subFiles != null) {
    
    
            for (File subFile : subFiles) {
    
    
                subDeleted &= deleteFileOrDir(subFile);
            }
        }
        return subDeleted ? file.delete() : false;
    }
}