我知道以前有人問過類似的問題，但確實沒有可行的解決方案。我正在通過 DownloadManager 下載多個 PDF 文件，我想將這些文件保存到應用程序內存的緩存文件夾中，但找不到任何方法。這是我的代碼：public class MainActivity extends AppCompatActivity {    Button btn;    DownloadManager downloadManager;    List<String> myList = new ArrayList<String>();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        myList.add("https://doc.lagout.org/programmation/Actionscript%20-%20Flash%20-%20Flex%20-%20Air/Flash%20Development%20for%20Android%20Cookbook%20-%20Labrecque%20-%20Packt%20%282011%29/Flash%20Development%20for%20Android%20Cookbook%20-%20Labrecque%20-%20Packt%20%282011%29.pdf");        myList.add("http://www.csc.kth.se/utbildning/kth/kurser/DD143X/dkand11/Group1Mads/andreas.ulvesand.daniel.eriksson.report.pdf");        myList.add("http://enos.itcollege.ee/~jpoial/allalaadimised/reading/Android-Programming-Cookbook.pdf");        myList.add("https://x.coe.phuket.psu.ac.th/warodom/242-320/ebook/9781785883262-ANDROID_PROGRAMMING_FOR_BEGINNERS.pdf");        myList.add("https://www.cs.cmu.edu/~bam/uicourse/830spring09/BFeiginMobileApplicationDevelopment.pdf");        myList.add("https://commonsware.com/Android/Android-1_0-CC.pdf");        btn = findViewById(R.id.download_btn);        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                downloadManager = (DownloadManager)getSystemService(Context.DOWNLOAD_SERVICE);                for(int i = 0; i < myList.size(); i++) {                    Uri uri = Uri.parse(myList.get(i));                    DownloadManager.Request request = new DownloadManager.Request(uri);                    request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);                    Long reference = downloadManager.enqueue(request);                }            }        });    }}