java - 为什么如果扩展抽象 BaseActivity 全局变量就会变成 null

Question

我有一个如下所示的 BaseActivity...其中父类(super class)光束上的我的接口(interface)全局对象为 null。

public abstract class BaseActivity extends BaseTabActivity { 
          //did some implementation
}


public abstract class BaseTabActivity extends BasePickerActivity {
    //did some implementation
}

public abstract class BasePickerActivity extends Activity {
   // This is an interface
       private IOnImagSelected iOnImagSelected;

       public void imagePicker(IOnImagSelected iOnImagSelected){
           this.iOnImagSelected = iOnImagSelected;
       }

        @Override
        protected void onActivityResult(int requestCode, int resultCode, Intent data) {
            // process data and called iOnImagSelected

                  // Here I get null point which mean iOnImagSelected is null
                          iOnImagSelected.onImageSelected(imagepath)
        }
}

现在我有一个类似的 Activity

public class MyActivity extends BaseActivity implements IOnImagSelected {

       public void onPickImageClick(View v){
           imagePicker(this);
        }

     @Override
     poublic void onImageSelected(){

       }

}

为什么我的接口(interface)变量变成了 null 。请帮我解决这个问题

Answer 1

由于我的 Google Nexus 7 开发者设置中的此选项，我解决了所有问题

转到设置->开发者选项

在应用程序类别中(向下滚动查看)，查看选项不要保留 Activity(一旦用户释放每个 Activity，就销毁它)。

I found this from this post

给那个人。:)