Java 如何在Android中以编程方式打开下载的文件？

使用这段代码，我可以从Android中的URL下载文件并将其保存到SD卡中，有没有任何方法可以通过编程方式打开此文件

@Override
protected Void doInBackground(Void... arg0) {
    DownloadFromUrl();
    return null;
}


public static void DownloadFromUrl() {

   try {
           File root = android.os.Environment.getExternalStorageDirectory();               

           File dir = new File (root.getAbsolutePath() + "/SDCard");
           if(dir.exists()==false) {
                dir.mkdirs();
           }

           URL url = new URL(DownloadUrl); //you can write here any link
           File file = new File(dir, fileName);

           long startTime = System.currentTimeMillis();
           Log.d("DownloadManager", "download begining");
           Log.d("DownloadManager", "download url:" + url);
           Log.d("DownloadManager", "downloaded file name:" + fileName);

           /* Open a connection to that URL. */
           URLConnection ucon = url.openConnection();

           /*
            * Define InputStreams to read from the URLConnection.
            */
           InputStream is = ucon.getInputStream();
           BufferedInputStream bis = new BufferedInputStream(is);

           /*
            * Read bytes to the Buffer until there is nothing more to read(-1).
            */
           ByteArrayBuffer baf = new ByteArrayBuffer(5000);
           int current = 0;
           while ((current = bis.read()) != -1) {
              baf.append((byte) current);
           }

           /* Convert the Bytes read to a String. */
           FileOutputStream fos = new FileOutputStream(file);
           fos.write(baf.toByteArray());
           fos.flush();
           fos.close();
           Log.d("DownloadManager", "download ready in" + ((System.currentTimeMillis() - startTime) / 1000) + " sec");




   } catch (IOException e) {
       Log.d("DownloadManager", "Error: " + e);
   }

}


}

意图能在这方面有所帮助吗

private static class Task extends AsyncTask<Void, Void, Void> {

    static String DownloadUrl = "http://00.00.00.00/abc.crt";
    static String fileName = "def.crt";

@Override
protected Void doInBackground(Void... arg0) {
    DownloadFromUrl();
    return null;
}


public static void DownloadFromUrl() {

   try {
           File root = android.os.Environment.getExternalStorageDirectory();               

           File dir = new File (root.getAbsolutePath() + "/SDCard");
           if(dir.exists()==false) {
                dir.mkdirs();
           }

           URL url = new URL(DownloadUrl); //you can write here any link
           File file = new File(dir, fileName);

           long startTime = System.currentTimeMillis();
           Log.d("DownloadManager", "download begining");
           Log.d("DownloadManager", "download url:" + url);
           Log.d("DownloadManager", "downloaded file name:" + fileName);

           /* Open a connection to that URL. */
           URLConnection ucon = url.openConnection();

           /*
            * Define InputStreams to read from the URLConnection.
            */
           InputStream is = ucon.getInputStream();
           BufferedInputStream bis = new BufferedInputStream(is);

           /*
            * Read bytes to the Buffer until there is nothing more to read(-1).
            */
           ByteArrayBuffer baf = new ByteArrayBuffer(5000);
           int current = 0;
           while ((current = bis.read()) != -1) {
              baf.append((byte) current);
           }

           /* Convert the Bytes read to a String. */
           FileOutputStream fos = new FileOutputStream(file);
           fos.write(baf.toByteArray());
           fos.flush();
           fos.close();
           Log.d("DownloadManager", "download ready in" + ((System.currentTimeMillis() - startTime) / 1000) + " sec");




   } catch (IOException e) {
       Log.d("DownloadManager", "Error: " + e);
   }

}


}

---

使用FileInputStream并将下载的文件加载到内存中

@Override
protected Void doInBackground(Void... arg0) {
    DownloadFromUrl();
    return null;
}


public static void DownloadFromUrl() {

   try {
           File root = android.os.Environment.getExternalStorageDirectory();               

           File dir = new File (root.getAbsolutePath() + "/SDCard");
           if(dir.exists()==false) {
                dir.mkdirs();
           }

           URL url = new URL(DownloadUrl); //you can write here any link
           File file = new File(dir, fileName);

           long startTime = System.currentTimeMillis();
           Log.d("DownloadManager", "download begining");
           Log.d("DownloadManager", "download url:" + url);
           Log.d("DownloadManager", "downloaded file name:" + fileName);

           /* Open a connection to that URL. */
           URLConnection ucon = url.openConnection();

           /*
            * Define InputStreams to read from the URLConnection.
            */
           InputStream is = ucon.getInputStream();
           BufferedInputStream bis = new BufferedInputStream(is);

           /*
            * Read bytes to the Buffer until there is nothing more to read(-1).
            */
           ByteArrayBuffer baf = new ByteArrayBuffer(5000);
           int current = 0;
           while ((current = bis.read()) != -1) {
              baf.append((byte) current);
           }

           /* Convert the Bytes read to a String. */
           FileOutputStream fos = new FileOutputStream(file);
           fos.write(baf.toByteArray());
           fos.flush();
           fos.close();
           Log.d("DownloadManager", "download ready in" + ((System.currentTimeMillis() - startTime) / 1000) + " sec");




   } catch (IOException e) {
       Log.d("DownloadManager", "Error: " + e);
   }

}


}

---

如果文件具有特定扩展名，则可能有其他加载方式，而不需要将其解析为字节数组

如何打开？作为文本、二进制或应用程序？是的，

意图

是一种方法；看看谷歌或谷歌。当你说“开放”时，你是什么意思？文件类型是什么（如What's.crt）？数据是什么？一串音频？感谢Udrian&Matt，理想情况下。CRT是VPN证书文件，安装后会弹出通知，输入证书名称，然后为Android VPN应用程序安装文件。我想如果我们想读取一个文件，那么我们需要FileInputStream来打开这个文件，不应该使用它吗？GJordis它将作为二进制文件打开，当openedI不知何故错过了一个.CRT文件时，它将调用VPN应用程序。是的，如果您的意图是提示用户在应用程序之外打开此文件，那么您应该使用意图。这可能会对您有所帮助，谢谢Udrian，我尝试了同样的方法，但由于我使用的是异步任务，因此它不允许我在那里调用intent<代码>文件videoFile2Play=新文件（“/sdcard/nice_movie.mpeg”）；意图i=新意图（）；i、 setAction（android.content.Intent.ACTION\u视图）；i、 setDataAndType（Uri.fromFile（videoFile2Play），“video/mpeg”）；星触觉（i）@Override protected Void doInBackground(Void... arg0) { DownloadFromUrl(); return null; } public static void DownloadFromUrl() { try { File root = android.os.Environment.getExternalStorageDirectory(); File dir = new File (root.getAbsolutePath() + "/SDCard"); if(dir.exists()==false) { dir.mkdirs(); } URL url = new URL(DownloadUrl); //you can write here any link File file = new File(dir, fileName); long startTime = System.currentTimeMillis(); Log.d("DownloadManager", "download begining"); Log.d("DownloadManager", "download url:" + url); Log.d("DownloadManager", "downloaded file name:" + fileName); /* Open a connection to that URL. */ URLConnection ucon = url.openConnection(); /* * Define InputStreams to read from the URLConnection. */ InputStream is = ucon.getInputStream(); BufferedInputStream bis = new BufferedInputStream(is); /* * Read bytes to the Buffer until there is nothing more to read(-1). */ ByteArrayBuffer baf = new ByteArrayBuffer(5000); int current = 0; while ((current = bis.read()) != -1) { baf.append((byte) current); } /* Convert the Bytes read to a String. */ FileOutputStream fos = new FileOutputStream(file); fos.write(baf.toByteArray()); fos.flush(); fos.close(); Log.d("DownloadManager", "download ready in" + ((System.currentTimeMillis() - startTime) / 1000) + " sec"); } catch (IOException e) { Log.d("DownloadManager", "Error: " + e); } } }