Thank you everyone! Solved
//Copy assets large files to local SD card

public static void CopyAssets(Context context, String assetDir, String dir) { String[] files; try { files = context.getResources().getAssets().list(assetDir); } catch (IOException e1) { return; } File mWorkingPath = new File(dir); // if this directory does not exists, make one. if (!mWorkingPath.exists()) { if (!mWorkingPath.mkdirs()) { } } for (int i = 0; i < files.length; i++) { try { String fileName = files[i]; // we make sure file name not contains '.' to be a folder. if (!fileName.contains(".")) { if (0 == assetDir.length()) { CopyAssets(context, fileName, dir + fileName + "/"); } else { CopyAssets(context, assetDir + "/" + fileName, dir+ fileName + "/"); } continue; } File outFile = new File(mWorkingPath, fileName); if (outFile.exists()) outFile.delete(); InputStream in = null; if (0 != assetDir.length()) in = context.getAssets().open(assetDir + "/" + fileName); else in = context.getAssets().open(fileName); OutputStream out = new FileOutputStream(outFile); // Transfer bytes from in to out byte[] buf = new byte[1024]; int len; while ((len = in.read(buf)) > 0) { out.write(buf, 0, len); } in.close(); out.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }

For file stream operations, if it is an entire folder, it needs to be traversed and copied to the specified directory under the SD card.

A single file looks like this, and the entire directory is traversed recursively (the folder directory must exist, if it does not exist, you need to create the directory manually):

InputStream is = context.getResources().getAssets().open("你的文件") FileOutputStream fos = new FileOutputStream("指定的文件目录"); byte[] buffer = new byte[8192]; int count; while ((count = is.read(buffer)) > 0){ fos.write(buffer, 0, count); } fos.close(); is.close();

A single file of 40M may cause problems, and the compilation may not pass. It is best to split it into small files (1M), assemble it with RandomAccessFile and write it to the SD card. The idea is this, the specific IO operations will not be listed in detail.

File stream, sub-thread

Isn’t it really called aassetsfolder? . Then just traverse and write to the SD card in the sub-thread.