Android 保存文件demo

Android 保存文件通常涉及到两个关键步骤：获取存储权限和实际写入文件。这里有一个简单的示例演示如何在Android应用中读取并写入文件：

// 1. 请求存储权限 (如果尚未请求)
if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
        != PackageManager.PERMISSION_GRANTED) {
    ActivityCompat.requestPermissions(this,
            new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
            MY_PERMISSIONS_REQUEST_WRITE_EXTERNAL_STORAGE);
} else {
    // 如果已授权，可以继续操作
}

// 2. 获取外部存储目录 (Environment.getExternalStorageDirectory())
FileOutputStream outputStream = null;
try {
    File file = new File(getExternalFilesDir(Environment.DIRECTORY_DOCUMENTS), "example.txt");
    FileOutputStream fos = openFileOutput(file.getName(), MODE_PRIVATE);
    outputStream = fos;

    // 写入数据
    byte[] data = "这是要保存的数据".getBytes();
    outputStream.write(data);
    outputStream.flush(); // 确保数据写入

    Log.d("SaveFile", "文件保存成功");
} catch (IOException e) {
    e.printStackTrace();
} finally {
    if (outputStream != null) {
        try {
            outputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

// 3. 可选的：检查文件是否已保存并读取（用于测试）
try {
    FileInputStream fis = openFileInput(file.getName());
    BufferedReader br = new BufferedReader(new InputStreamReader(fis));
    StringBuilder contentBuilder = new StringBuilder();
    String line;
    while ((line = br.readLine()) != null) {
        contentBuilder.append(line);
    }
    String savedContent = contentBuilder.toString();
    Log.d("SaveFile", "保存的内容: " + savedContent);
} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
}