从使用该方法之外的变量的其他类中调用方法 [英] Calling a method from a different class that uses variables outside the method

问题描述

我有问题.我在这样的类中有一个方法:

I have a problem. I have a method in a class like this:

public void UpdateActionBar(int CurrentFragmentNum)
{
    if (CurrentFragmentNum == 1)
    {
        btnBack.Visibility = ViewStates.Invisible;
        btnNext.Visibility = ViewStates.Invisible;
    }
    else
    {
        btnBack.Visibility = ViewStates.Visible;
        btnNext.Visibility = ViewStates.Visible;
    }

    if (CurrentFragmentNum == 3)
    {
        btnNext.Text = "Finish";
    }
    else
    {
        btnNext.Text = "Next";
    }
}

现在在另一个类中，我这样调用此方法:

Now in another class I call this method like this:

new ActionBar_Setup().UpdateActionBar(CurrentFragmentNum);

但是正如您所见，我使用了2个变量: btnBack 和 btnNext 当我从不同的类调用方法时，这些变量为null，因为未定义变量.但是我无法移动为这些变量分配值的行，因为它使用了视图变量.这是显示我的意思的代码:

But as you an see I use the 2 variables: btnBack and btnNext Those variables are null when I call the method from a different class, because then the variables are not defined. But I can't move the lines that assign a value to those variables because it uses a view variable. Here is the code to show what I mean:

public class ActionBar_Setup : Android.Support.V4.App.Fragment
{
    Button btnBack;
    Button btnNext;

    public int CurrentFragmentNum = 1;
    public int PreviousFragmentNum = 1;
    public string Direction;

    public override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
    }

    public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
    {
        View view = inflater.Inflate(Resource.Layout.setup_nav_bar, container, false);

        btnBack = view.FindViewById<Button>(Resource.Id.btnBack);
        btnNext = view.FindViewById<Button>(Resource.Id.btnNext);

        btnBack.Click += btnBack_Click;
        btnNext.Click += btnNext_Click;

        UpdateActionBar(CurrentFragmentNum);

        return view;
    }

    public void btnBack_Click(object sender, EventArgs e)
    {
        if (CurrentFragmentNum > 1)
        {
            PreviousFragmentNum = CurrentFragmentNum;
            CurrentFragmentNum -= 1;
            Direction = "Backwards";
            UpdateActionBar(CurrentFragmentNum);
            (Activity as MainActivity)?.ShowFragment(CurrentFragmentNum, PreviousFragmentNum, Direction);
        }
    }

    public void btnNext_Click(object sender, EventArgs e)
    {
        if (CurrentFragmentNum < 3)
        {
            PreviousFragmentNum = CurrentFragmentNum;
            CurrentFragmentNum += 1;
            Direction = "Forwards";
            UpdateActionBar(CurrentFragmentNum);
            (Activity as MainActivity)?.ShowFragment(CurrentFragmentNum, PreviousFragmentNum, Direction);
        }
    }

    public void UpdateActionBar(int CurrentFragmentNum)
    {
        if (CurrentFragmentNum == 1)
        {
            btnBack.Visibility = ViewStates.Invisible;
            btnNext.Visibility = ViewStates.Invisible;
        }
        else
        {
            btnBack.Visibility = ViewStates.Visible;
            btnNext.Visibility = ViewStates.Visible;
        }

        if (CurrentFragmentNum == 3)
        {
            btnNext.Text = "Finish";
        }
        else
        {
            btnNext.Text = "Next";
        }
    }
}

如何解决此问题，以便可以在其他类中调用该函数?

How can I fix this, so I can call the function in a different class?

推荐答案

您可以将您的 ActionBar_Setup 单身:

public class ActionBar_Setup : Android.Support.V4.App.Fragment
 {

    public static ActionBar_Setup Instance;
    public static ActionBar_Setup NewInstance()
    {
        if (Instance== null)
        {
            Instance= new ActionBar_Setup();

        }

        return Instance;
    }
    ...
}

然后在创建 ActionBar_Setup 时，如下所示:

then when you create the ActionBar_Setup like this:

ActionBar_Setup fActionBarSetup = ActionBar_Setup.NewInstance();

最终在其他类中调用 UpdateActionBar 方法，如下所示:

finally call UpdateActionBar method in other class like this:

ActionBar_Setup.Instance.UpdateActionBar(3);

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