首先是下載：

public static void downLoadFromStream(final String urlString, final String fileType, final String resourceId) {
        final ProgressDialog progressDialog = new ProgressDialog(webView.getContext());
        progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        progressDialog.setCancelable(false);
        progressDialog.setCanceledOnTouchOutside(false);
        progressDialog.setMessage("檔案獲取中，請稍候.....");
        progressDialog.show();
        String dirPath = "";
        dirPath =  Environment.getExternalStorageDirectory() + File.separator+"download"+File.separator
        //建立檔案下載的目錄
        final File dir = new File(dirPath); 
        if (!dir.exists()) {
            dir.mkdirs();
        }
        final Runnable runnable = new Runnable() {
            @Override
            public void run() {
                int byteread = 0;
                try {
                    final String fileName = resourceId + "." + fileType;//把resourceId 與filetype拼接成檔案的名稱
                    final File file = new File(dir, fileName); //在剛剛建立好的目錄下建立檔案
                    file.createNewFile();
                    final URL url = new URL(urlString);
                    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                    InputStream inputStream = connection.getInputStream();
                    OutputStream outputStream = new FileOutputStream(file);
                    byte buffer[] = new byte[4 * 1024];
                    while ((byteread = inputStream.read(buffer)) != -1) {
                        outputStream.write(buffer, 0, byteread);
                    }
                    outputStream.close();
                    inputStream.close();
                    connection.disconnect();
                    progressDialog.dismiss();

                   openFile(webView.getContext(), file);
                    
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        };
        new Thread(runnable).start();
    }
 

這裡 需要注意：可以先判斷

if(connection.getContentLength() >0){
                        
  }

再去接受檔案流。但是有些情況伺服器端不返回ContentLength，所以這個事先跟服務端約定好。如果是別人的服務的話有請求連結用瀏覽器開啟看看請求就知道了（之後會寫個部落格說說我的理解）

2、

接下來是開啟檔案

先來個腦殘版的，這個相當的坑，從網上考過來的。

private static void openFile(Context context, File f) {
        Intent myIntent = new Intent(android.content.Intent.ACTION_VIEW);
        String  mimetype = getMIMEType(f);
        myIntent.setDataAndType(Uri.fromFile(f),mimetype);
        context.startActivity(myIntent);
    }
 

 /* 判斷檔案MimeType的method */
    private static String getMIMEType(File f) {
        String type = "";
        String fName = f.getName();
  /* 取得副檔名 */
        String end = fName.substring(fName.lastIndexOf(".")
                + 1, fName.length()).toLowerCase();

  /* 依副檔名的型別決定MimeType */
        if (end.equals("m4a") || end.equals("mp3") || end.equals("mid") ||
                end.equals("xmf") || end.equals("ogg") || end.equals("wav")) {
            type = "audio";
        } else if (end.equals("3gp") || end.equals("mp4")) {
            type = "video";
        } else if (end.equals("jpg") || end.equals("gif") || end.equals("png") ||
                end.equals("jpeg") || end.equals("bmp")) {
            type = "image";
        } else if (end.equals("wps")) {
            type = "application/vnd.ms-works";
        } else if (end.equals("doc")) {
            type = "application/msword";
        } else if (end.equals("docx")) {
            type = "application/vnd.openxmlformats-officedocument.wordprocessingml.document";
        } else if (end.equals("txt")) {
            type = "text/plain";
        } else if (end.equals("pdf")) {
            type = "application/pdf";
        } else if (end.equals("apk")) {
  /* android.permission.INSTALL_PACKAGES */
            type = "application/vnd.android.package-archive";
        } else {
            type = "*";
        }
  /*如果無法直接開啟，就跳出軟體列表給使用者選擇 */
        if (end.equals("apk")) {
        } else {
            type += "/*";
        }
        return type;
    }
 

來個漂亮的：

private static void openFile(Context context, File f) {
        Intent myIntent = new Intent(android.content.Intent.ACTION_VIEW);
        String extension = android.webkit.MimeTypeMap.getFileExtensionFromUrl(Uri.fromFile(f).toString());
        String mimetype = android.webkit.MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
        myIntent.setDataAndType(Uri.fromFile(f),mimetype);
        context.startActivity(myIntent);

    }

系統提供的解析檔案型別的方法，很強大。不會出現上述的情況了。