相关疑难解决方法(0)

我正在android环境中工作,并尝试了以下代码,但它似乎没有工作.

String [] stockArr = (String[]) stock_list.toArray();

如果我定义如下:

String [] stockArr = {"hello", "world"};

有用.有什么东西我不见了吗？

1. 没错

   Object[] a = new String[]{"12","34","56"};
   String[] b = (String[]) a;
   

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2. 没错

   Object a = new String[]{"12","34","56"};    
   String[] b = (String[]) a;
   

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3. 运行时错误:ClassCastException

   Object[] a = new Object[3];
   a[0] = "12";
   a[1] = "34";
   a[2] = "56";
   String[] b = (String[]) a;
   

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4. 运行时错误:ClassCastException

   Object[] a = {"12","34","56"};    
   String[] b = (String[]) a;
   

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当然,如果将Object[]变量String[]创建为一个变量,我们可以将变量转发回String[].

我的问题是,为什么我们不能投Object[]来String[],当它被作为创建的Object[],但它的所有成员都是字符串？是因为安全原因还是没有那么有用呢？

在我的应用程序中,我为gcm ccs(xmpp)运行这些代码,代码显示以下错误执行时发生错误doinbackground.excute() 这是代码:

sendTask = new AsyncTask<String, String, String>() {
    protected String doInBackground(String... title) {

        Bundle data = new Bundle();
        data.putString("ACTION", action);
        data.putString("CLIENT_MESSAGE", "Hello GCM CCS XMPP!");
        String id = Integer.toString(ccsMsgId.incrementAndGet());

        try {
            Log.d("RegisterActivity", "messageid: " + id);
            gcm.send(SENDER_ID + "@gcm.googleapis.com", id,
                     data);
            Log.d("RegisterActivity", "After gcm.send successful.");
        } catch (IOException e) {
            Log.d("RegisterActivity", "Exception: " + e);
            e.printStackTrace();
        }
        return "Sent message.";
    }

    protected void onPostExecute(String result) {
        sendTask = null;
        // tosat about the success in return
    } …