Question

我正在开发一个BlackBerry应用程序，它通过HTTP请求（javax.microedition.io.HttpConnection）与服务器通信。在设备上，用户单击一些UI项，设备将请求发送到服务器，当响应到来时，UI更改。通信在新线程下进行，而UI线程则推送并弹出ProgressDialogScreen。

问题有时候，当响应出现并且弹出ProgressDialogScreen时，UI不会改变，但是几秒钟之后UI会发生变化。如果您在弹出ProgressDialogScreen和推送新屏幕之间请求，则会出现问题。推出第一个最古老的新屏幕，推出最新的新屏幕。这种情况可以像服务器响应错误请求一样被观察到。这个问题发生在模拟器和设备上。

另一个问题是，一个请求有时会返回两个相同的响应。我能够在日志的模拟器上看到这两个问题，但我无法在设备上看到这个问题，因为我看不到日志。

修改

String utf8Response;
HttpConnection httpConn = null;
try{
    httpConn = (HttpConnection) Connector.open(url);
    httpConn.setRequestMethod(HttpConnection.GET);
    httpConn.setRequestProperty("Content-Type", "text/html; charset=UTF8");
    if(sessionIdCookie != null){
        //may throw IOException, if the connection is in the connected state.
        httpConn.setRequestProperty("Cookie", sessionIdCookie);
    }
}catch (Exception e) {
    //...
}

try{
    httpConn.getResponseCode();
    return httpConn;
}catch (IOException e) {
    // ...
}
byte[] responseStr = new byte[(int)httpConn.getLength()];
DataInputStream strm = httpConn.openDataInputStream();
strm.readFully(responseStr);
try{
    strm.close();
}catch (IOException e) {
    // ....
}
utf8Response = new String(responseStr, "UTF-8");

如果此代码成功运行，则会运行此代码并按下新屏幕：

UiApplication.getUiApplication().invokeLater(new Runnable() {
    public void run() {
       Vector accounts = Parser.parse(utf8Response,Parser.ACCOUNTS);
       if (accounts.size() == 0){
           DialogBox.inform(Account.NO_DEPOSIT);
           return;
       }
       currentScreen = new AccountListScreen(accounts);
       changeScreen(null,currentScreen);
    }
});

public void changeScreen(final AbstractScreen currentScreen,final AbstractScreen nextScreen) {
    if (currentScreen != null) 
        UiApplication.getUiApplication().popScreen(currentScreen);
    if (nextScreen != null)
        UiApplication.getUiApplication().pushScreen(nextScreen);
}

EDITv2：

private static void progress(final Stoppable runThis, String text,boolean cancelable) {
    progress = new ProgressBar(runThis, text,cancelable);
    Thread threadToRun = new Thread() {
        public void run() {
            UiApplication.getUiApplication().invokeLater(new Runnable() {
                public void run() {
                    try{
                        UiApplication.getUiApplication().pushScreen(progress);
                    }catch(Exception e){
                        Logger.log(e);
                    }
                }
            });
            try {
                runThis.run();
            } catch (Throwable t) {
                t.printStackTrace();
            }
            UiApplication.getUiApplication().invokeLater(new Runnable() {
                 public void run() {
                    try {
                        UiApplication.getUiApplication().popScreen(progress);
                    } catch (Exception e) { }
                 }
            });
        }
   };
   threadToRun.start();
}

顺便说一下，ProgressBar从net.rim.device.api.ui.container.PopupScreen延伸，Stoppable从Runnable延伸

Answer 1

我准备在准备并推送新屏幕后弹出进度条。这样，请求和响应之间就不会有新的请求。

Answer 2

为什么不这样做：

private static void progress(final Stoppable runThis, String text,boolean cancelable) {
    progress = new ProgressBar(runThis, text,cancelable);
    UiApplication.getUiApplication().pushScreen(progress);
    [...]

Answer 3

好像你正在UI线程上进行解析。请从ui线程中删除Vector accounts = Parser.parse(utf8Response,Parser.ACCOUNTS);并在单独的线程中执行。

黑莓多线程问题

3 个答案: