我如何從另一個 class 訪問 MainActivity object

Question

在我的 MainActivity class 我有 object ExpandableListViewAdapter mExpandableListViewAdapter 我需要它在不同的類（非活動）中使用它。 這個 object 在 mainActivity 中初始化，之后我想在另一個 class 中使用他的一種方法。 如何將這個 object 傳遞給另一個 class？ 我在想我可以使用一個界面

    public class MainActivity extends AppCompatActivity  {
    private static final Logger LOG = LoggerFactory.getLogger("MainActivity");

    private ExpandableListView mExpandableListView;
    private ExpandableListViewAdapter mExpandableListViewAdapter;
    private List<String> mListDataGroup;
    private HashMap<String, List<String>> mListDataChild;
    PreselectionAplicationUseCases preselectionAplicationUseCases;


    private void unselectPrevious (int childId)
    {
     setContentView(R.layout.activity_main);


    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initViews();
        initListeners();
        initObjects();
        initListData();
    }

    private void initViews() {
     mExpandableListView = findViewById(R.id.expandableListView);
    }

     private void initListeners() {
    int i= 0;

    mExpandableListView.setOnChildClickListener((parent, v, groupPosition, childPosition, id) -> {

        String title = mListDataChild.get(mListDataGroup.get(groupPosition)).get(childPosition);
        if (Constants.PROPIETARY_SELECTION_SUPPORTED == false)
        {
            if (groupPosition > 1)
                groupPosition -=1;
        }

        if (groupPosition == 0) {
            switch (childPosition) {
                case 0:
                    if (!isServiceRunning()) {
                        startService();
                    }
                    break;

                case 1:
                    if (isServiceRunning()) {
                        stopService();
                    }
                    break;
            }
        }else if (groupPosition == 1) { 
            int selection = 0;
            selection = mExpandableListViewAdapter.getSelectedChild();
            if (selection == -1)
            {
                mExpandableListViewAdapter.setSelectedChild(childPosition);
                TransactionState.setUserPreferredAid(aidList.get(childPosition));
            }
            else{
                if (childPosition == selection)
                {
                  
                    mExpandableListViewAdapter.setSelectedChild(-1);
                    TransactionState.setUserPreferredAid(null);
                }else {
                    // Deselect previous and select new
                    mExpandableListViewAdapter.setSelectedChild(childPosition);
                    TransactionState.setUserPreferredAid(aidList.get(childPosition));
                }
            }
            mExpandableListViewAdapter.notifyDataSetChanged();


        }else if (groupPosition == 2) {
            if (childPosition == 0) {
                startActivity(new Intent(Settings.ACTION_LOCALE_SETTINGS));
            }
        } else if (groupPosition == 3) {
                    showContact(title);
            }
        } else if (groupPosition == 4) {
            if (childPosition == 0) {
                HTMLPrinter htmlPrinter= HTMLPrinter.getInstance();
                htmlPrinter.ticketTest();
            }
        } 

        return false;
    });
    

}

private void initObjects() {
    // initializing the list of groups
    mListDataGroup = new ArrayList<>();

    // initializing the list of child
    mListDataChild = new HashMap<>();

    // initializing the adapter object
    mExpandableListViewAdapter = new ExpandableListViewAdapter(this, mListDataGroup, mListDataChild);

    // setting list adapter
    mExpandableListView.setAdapter(mExpandableListViewAdapter);

}
}

Answer 1

將您的非活動 class 視為 Foo。

class Foo{
   
    private AdapterObj mAdapterObj;
    public void setAdapterObj(AdapterObj adapterObj){
       this.mAdapterObj=adapterObj
   }
   ......

}

從 MainActivity 傳遞您的 object 實例。

void initViews(){
  Foo obj=new Foo();
  obj.setAdapterObj(myAdapterObj);
}