android - 如何将 Activity 实例传递给另一个 Activity

Question

您好，我有一个名为 BaseActivity 的 Activity ，它扩展了 Activity。从这里我必须去 SettingsActivity 它扩展了 PreferenceActivity，按下菜单按钮。要启动一个位于独立类中的 AsyncTask，我需要一个 BaseActivity 实例。如何在 SettingsActivity 中获取 BaseActivity 实例？

有没有办法，例如:

intent.putExtra("activity_instance",BaseActivity.this);

Answer 1

使用 getter 和 setter 并将它们所在的类作为单例类。

这是一个单例类。使用这个类，我们可以在整个类中共享数据(例如:int、boolean、activity 实例...等)。

public class CommonModelClass 
{
    public static CommonModelClass singletonObject;
    /** A private Constructor prevents any other class from instantiating. */

  private Activity baseActivity; 

    public CommonModelClass() 
    {
        //   Optional Code
    }
    public static synchronized CommonModelClass getSingletonObject() 
    {
        if (singletonObject == null) 
        {
            singletonObject = new CommonModelClass();
        }
        return singletonObject;
    }


    /**
     * used to clear CommonModelClass(SingletonClass) Memory
     */ 
     public void clear()  
      {  
         singletonObject = null;  
      }


    public Object clone() throws CloneNotSupportedException 
    {
        throw new CloneNotSupportedException();
    }

    //getters and setters starts from here.it is used to set and get a value

    public Activity getbaseActivity()
    {
        return baseActivity;
    }

    public void setbaseActivity(Activity baseActivity)
    {
        this.baseActivity = baseActivity;
    }   

}       

在 BaseActivity 类中这样做。

         Class BaseActivity extends Activity{


                @Override
                protected void onCreate(Bundle savedInstanceState) {

                    CommonModelClass commonModelClass = CommonModelClass.getSingletonObject();

    commonModelClass.setbaseActivity(BaseActivity.this);

//after using the BaseActivity instance dont forget to call commonModelClass.clear(); else it wont be garbage collected         


               }

            }

在 SettingsActivity 中这样做

 Class SettingsActivity extends Activity{

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            CommonModelClass commonModelClass = CommonModelClass.getSingletonObject();



            Activity instanceBaseActivity=  commonModelClass.getbaseActivity();;


       }

    }

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