思路是：第一獲取要下載文件的大小，設為X，第二通過多線程監測已下載文件的大小，設為Y。Y/x就是下載的進度。關鍵代碼例如以下

//獲取要下載的object的metadata
    	ObjectMetadata tmpMetadata = client.getObjectMetadata(bucketName, key);
    	final long filesize = tmpMetadata.getContentLength();
    	final File downloadFile = new File(filename);
    	Thread t = new Thread(new Runnable() {
			
			@Override
			public void run() {
				while(true){
			   		 try {
							Thread.sleep(100);
						} catch (InterruptedException e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						}
			   		 System.out.println(downloadFile.getName()+"下載的進度為："+ (float)downloadFile.length()*100/filesize);
			   		 if(downloadFile.length()==filesize)
			   			 break;
			   	 }
			}
		});
   	 	t.start();
   	 	//下載object
    	 ObjectMetadata  result =client.getObject(new GetObjectRequest(bucketName, key),downloadFile);

阿裏雲 oss 文件下載進度顯示