Question

我写了下面这段代码。它用于创建相机播放器。我在诺基亚手机上测试过它。它工作正常，我能够看到相机并使用它的功能。

但问题是，当代码在三星手机上测试时，它会引发Media异常并最终不得不退出应用程序。由于这个代码，我内置的相机功能（即在三星手机上）也停止工作。那是什么原因呢？

    public void startCamera()
{
    try
    {
        try 
        {
            // if player==null
            player = createPlayer();
        } 
        catch (Exception ex) 
        {
            ex.printStackTrace();
            ErrorDialog.show(ex, "We are exiting the application.",
                        "Exit", new com.auric.qrev.scanqrcode.lwuit.ui.Action(){
                    public void actionPerformed() {
                        m_objMIDlet.exitApp();
                    }
            });
        }
        try 
        {
            player.realize(); 
            player.prefetch();
        }
        catch (MediaException ex) 
        {
            ex.printStackTrace();
            ErrorDialog.show(ex, "We are exiting the application.",
                        "Exit", new com.auric.qrev.scanqrcode.lwuit.ui.Action(){
                    public void actionPerformed() {
                        m_objMIDlet.exitApp();
                    }
            });
        }




        //Grab the video control and set it to the current display.
        videoControl = (VideoControl)(player.getControl("VideoControl"));
        if (videoControl == null)
        {
            //discardPlayer();
            stopCamera();
            ErrorDialog.show("Unsupported:\n"+
                 "Can't get video control\n"+
                 "We are exiting the application.",
                    "Exit", new com.auric.qrev.scanqrcode.lwuit.ui.Action(){
                public void actionPerformed() {
                    m_objMIDlet.exitApp();
                }
            });
        }

        mediaComponent = new MediaComponent(player);
        mediaComponent.setFocusable(false);
        m_cameraScreen.showCamera(mediaComponent);
        start();
    }
    catch(Exception ex)
    {
        ex.printStackTrace();
        //discardPlayer();
        stopCamera();
        ErrorDialog.show("Sorry,Resources unavailable.\nWe are exiting the application.",
                        "Exit", new com.auric.qrev.scanqrcode.lwuit.ui.Action(){
                    public void actionPerformed() {
                        m_objMIDlet.exitApp();
                    }
        });
    }

}

    private Player createPlayer()throws MediaException, Exception 
{
    Player mPlayer = null;
    // try capture://image first for series 40 phones
    try 
    {
        mPlayer = Manager.createPlayer("capture://image");
    }
    catch (Exception e) 
    {
        e.printStackTrace();
    }
    catch (Error e) 
    {
        e.printStackTrace();
    }

    // if capture://image failed, try capture://video
    if (mPlayer == null) 
    {
        try 
        {
            mPlayer = Manager.createPlayer("capture://video");
        } 
        catch (Exception e)
        {
            e.printStackTrace();
            throw new MediaException("Sorry,Resources unavailable.");
        }
    }

    if(mPlayer == null)
        throw new Exception("Sorry,Resources unavailable.");

    return mPlayer;

}

Answer 1

首先，您必须意识到printStackTrace()在模拟器之外几乎没用，除非您使用的是Symbian手机。

您也可以使用java.lang.Throwable代替Exception和Error

您可以通过以String收集信息并在测试时将其附加到简单的lcdui Form来确切了解发生了什么：


try {
    // do something that could potentially fail
} catch (Throwable th) {
    myDebugLcduiForm.append("potential failure number xx." + th + th.getMessage());
    // if necessary, throw a new RuntimeException
}

一旦确切知道哪行代码会引发异常，您可能希望更新/重新发布您的问题。

无法在j2me上打开三星手机上的相机

1 个答案: