android 读取u盘指定路径的文件

您可以使用Android提供的Storage Access Framework (SAF) API来读取U盘中指定路径的文件。

以下是示例代码：

// 在activity中启动SAF API
private static final int READ_REQUEST_CODE = 42;
public void openDocumentTree() {
    Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
    startActivityForResult(intent, READ_REQUEST_CODE);
}

// 处理SAF API回调
@Override
public void onActivityResult(int requestCode, int resultCode, Intent resultData) {
    if (requestCode == READ_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
        Uri treeUri = resultData.getData();
        DocumentFile pickedDir = DocumentFile.fromTreeUri(this, treeUri);

        // 指定路径下的文件夹名称和文件名称
        String folderName = "example_folder";
        String fileName = "example_file.txt";

        // 获取指定文件夹
        DocumentFile folder = pickedDir.findFile(folderName);
        if (folder != null && folder.isDirectory()) {
            // 获取指定文件
            DocumentFile file = folder.findFile(fileName);
            if (file != null && file.isFile()) {
                // 读取文件内容
                try {
                    InputStream inputStream = getContentResolver().openInputStream(file.getUri());
                    BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
                    StringBuilder stringBuilder = new StringBuilder();
                    String line;
                    while ((line = reader.readLine()) != null) {
                        stringBuilder.append(line);
                        stringBuilder.append("\n");
                    }
                    String fileContent = stringBuilder.toString();
                    // 处理文件内容
                    // ...
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

注意：您需要在AndroidManifest.xml文件中添加以下权限：

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />