c# - 在 Xamarin Android 中访问 UI 线程

Question

我的应用程序发送和接收 TCP 字符串。其中一个字符串是根据字符串使对象可见。我当前的代码给出 System.NullReferenceException has been throwed Object reference not set to an instance of an object.

我找不到正确的访问方法，我猜是因为 RunOnUI 似乎没有访问权限。

我当前的代码:

听众类:(完整类的片段，如果需要我可以发布更多)。

public void ReadCallback(IAsyncResult ar)
{
    MainActivity ma = new MainActivity();
    String content = string.Empty;

    StateObject so = (StateObject)ar.AsyncState;
    Socket handle = so.workSocket;

    int bytesRead = handle.EndReceive(ar);

    if (bytesRead > 0)
    {
        so.sb.Append(System.Text.Encoding.ASCII.GetString(so.buffer, 0, bytesRead));
        content = so.sb.ToString();
    }
    if (content.IndexOf("0") > -1)
    {
        ma.RunOnUiThread(() =>
        {
            //This is where the received data is passed
            ma.SortData(content);
        });
        Send(handle, content);
    }
    else
    {
        handle.BeginReceive(so.buffer, 0, StateObject.BufferSize, 0, new AsyncCallback(ReadCallback), so);
    }
}

以及 SortData 的代码:

public void SortData(string data)
{
    if(data == "0")
    {
        txtmsg.Visibility = ViewStates.Invisible;        
    }
} //This is the only code that's called, the txtmsg.Visibility part is the error producer once called. 

Answer 1

您必须在构造函数中将 Context 传递给您的类

所以你会在你的类中添加一个构造函数，比如:

MainActivity mContext;

public YourClass(MainActivity context) {
       this.mContext = context;
}

然后从您的类中调用该方法，例如:

mContext.RunOnUiThread(() =>
     {
       //This is where the received data is passed
       mContext.SortData(content);
     });