如何在不创建要调用的活动的新对象的情况下从另一个活动调用一个活动的功能？

Question

I created activity1 and called activity2 from the activity1 .Now i wish to call function of activity1 staying at activity2 and "without initializing instant of activity1 " in order to avoid recreated of activity 1 again.I want to know the code in callfirst() of my second activity

here is my mainactivity

    protected override void OnCreate (Bundle bundle)
    {
        base.OnCreate (bundle);
        SetContentView (Resource.Layout.Main);
        Button button1 = FindViewById<Button> (Resource.Id.myButton1);
        button1.Click += (object sender, EventArgs e) => firstload ();
    }
    protected override void OnSaveInstanceState (Bundle outState)
    {
        base.OnSaveInstanceState (outState);
    }
    public void firstload()
    {
        StartActivity(typeof(first));
    }

here is my first activity

    public class first : Activity
{
    protected override void OnCreate (Bundle bundle)
    {
        base.OnCreate (bundle);
        SetContentView (Resource.Layout.first);
        Button btn = FindViewById<Button>(Resource.Id.btnfirst);
        btn.Click += (object sender, EventArgs e) => loadsecond();
    }

    public void loadsecond()
    {
        StartActivity (typeof(second));
    }
     public void message()
    {
        Toast.MakeText (this, "fxn of activityfirst called from     activitysecond", ToastLength.Short).Show ();        
    }
}

here is my second activity

public class second : Activity
{

    protected override void OnCreate (Bundle bundle)
    {
        base.OnCreate (bundle);
        SetContentView (Resource.Layout.second);
        Button btn = FindViewById<Button> (Resource.Id.btnsecond);
        btn.Click += (object sender, EventArgs e) => callfirst();       
    }
    public void callfirst()
    {
      //what should i do here ???
    }

}

Answer 1

if you need to use some common functions and global variables, better create a class that holds them - like Globals.java . There you can have your global variables:

public static String someGlobalString = "";
public static void someGlobalFunction(){ };

and you can call them from your code like:

Globals.someGlobalString = "some value";
Globals.someGlobalFunction();

Answer 2

创建该方法static并使用该类名本身进行调用，因为static方法和变量从该类名本身进行调用

Answer 3

aYou can indeed use static methods for this purpose, but you should not use activities for static methods to be used by other activities. That is not how they are supposed to work. They should be separate entities which can pass messages to each other using the Binder framework. If you do need to have access to the same method, then simply create another class which has that static method available to both activities.