使用异步任务在Android中刷新多个imageView？

Question

我要做的是在单个活动上播放视频，视频数量未定义，可以从 1 到 8，在我的情况下，视频是一个图像序列，其中每个图像都是从摄像头下载的互联网使用固定时间间隔。

做单个视频活动不是问题，我可以使用 ImageView 和 AsyncTask 来制作，当我尝试制作多个视频活动时，使用此方法的许多实例不起作用，只能播放一个视频。我不知道到底发生了什么，但我认为这可能是由于 UIThread 导致的与货币有关的问题。

这里使用的AsyncTask代码：

private class AsyncTask_LiveView extends AsyncTask<String, Integer, Void> 
{   
    private String sImageMessage = "";

    private final WeakReference<ImageView> imageViewReference;
    private Bitmap bmImage = null;
    private String url = "";
    private String usr = "";
    private String pwd = "";
    private utils u = new utils();

    public AsyncTask_LiveView(ImageView imageView, String Url, String Usr, String Pwd)
    {
        imageViewReference = new WeakReference<ImageView>(imageView);
        url = Url;
        usr = Usr;
        pwd = Pwd;
    }

    // automatically done on worker thread (separate from UI thread)
    @Override
    protected Void doInBackground(final String... args) 
    {
        while(!isCancelled())
        {
            if(isCancelled())
                 return null;

            SystemClock.sleep(200);

            Log.v("ImageDownload","test");
            bmImage = u.DownloadBitmapFromUrl(url, usr, pwd);

            publishProgress(0);
        }

        return null;
    }

    // can use UI thread here
    @Override
    public void onProgressUpdate(Integer... i)
    {
        Log.v("Image", "Setup Image");
        if (imageViewReference != null) {
            ImageView imageView = imageViewReference.get();
            if (imageView != null) {
                imageView.setImageBitmap(bmImage);
            }
        }
    }
 }

我以这种方式启动 AsyncTask：

    public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layoutliveviewdouble);

        this.imgV1 = (ImageView ) findViewById(R.id.imageView1);
    aTaskImgV1 = new AsyncTask_LiveView(imgV1,
                                        URL1,
                                        "",
                                        "");


    this.imgV2 = (ImageView ) findViewById(R.id.imageView2);
    aTaskImgV2 = new AsyncTask_LiveView(imgV2,
                                        URL2,
                                        "root",
                                        "jenimex123");

    aTaskImgV1.execute();
    aTaskImgV2.execute();
}

DownloadBitmapFromUrl 方法是：

public Bitmap DownloadBitmapFromUrl(String imageURL, final String usr, final String pwd) {  //this is the downloader method
    try {
        URL url = new URL(imageURL); 


        /* Open a connection to that URL. */
        HttpURLConnection ucon = (HttpURLConnection) url.openConnection();
        ucon.setRequestMethod("GET");
        ucon.setDoOutput(true);
        Authenticator.setDefault (new Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication (usr, pwd.toCharArray());
            }
        });
        ucon.connect();

        /*
         * 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(100000);
        int current = 0;
        while ((current = bis.read()) != -1) {
                baf.append((byte) current);
        }

        /* Convert the Bytes read to a String. */
        Bitmap bmp = BitmapFactory.decodeByteArray(baf.toByteArray(), 0, baf.length());

        return bmp;
    } catch (Exception e) {
            //Log.d("ImageManager", "Error: " + e);
        return null;
    }
}

有什么想法吗？

解决方案：(21/01/11)

线束：

Authenticator.setDefault (new Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication (usr, pwd.toCharArray());
            }
        });

正在制动机制。实际上，全局只能设置一个凭据对 a，而其他下载进程则停留在请求使用错误凭据的过程中。

解决办法是：

String authString = usr + ":" + pwd;
byte[] authEncBytes = Base64.encode(authString.getBytes(), Base64.DEFAULT);
String authStringEnc = new String(authEncBytes);
ucon = (HttpURLConnection) url.openConnection();

if(_usr != "")
   ucon.setRequestProperty("Authorization", "Basic " + authStringEnc);

谢谢大家。

Answer 1

我认为你应该为每个ImageView 使用唯一的AsyncTask_LiveView。

Answer 2

这个函数支持多线程吗？

bmImage = u.DownloadBitmapFromUrl(url, usr, pwd);

Answer 3

看起来您在 downloadBitmapFromUrl(..) 方法中调用的某些方法涉及某些公共对象的同步。尝试在此方法的每个部分添加一些额外的日志记录，看看每个线程卡在哪里。我会这样做：

public Bitmap downloadBitmapFromUrl(String imageURL, final String usr, final String pwd) {  //this is the downloader method
    try {
    ...
    Log.i(toString() + " in " + Thread.currentThread(), "is about to open connection...");
    HttpURLConnection ucon = (HttpURLConnection) url.openConnection();
    Log.i(toString() + " in " + Thread.currentThread(), "has opened connection");

    ...

等等。