Question

我正在尝试在我的应用程序中实现ActionBar。我的代码很好但是当我尝试加载项目时它给了我这个错误：

引起：java.lang.IllegalStateException：Action Bar Tab必须有一个回调，并强制关闭

如何实施回电？

import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentTransaction;
import android.os.Bundle;

public class MainResource extends Activity {

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        final ActionBar actionBar = getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        Tab tabA = actionBar.newTab();
        tabA.setText("Tab A");
        tabA.setTabListener(new TabListener<Categories>(this, "Tag A", Categories.class));
        actionBar.addTab(tabA);

        Tab tabB = actionBar.newTab();
        tabB.setText("Tab B");
        tabB.setTabListener(new TabListener<Favourites>(this, "Tag B", Favourites.class));
        actionBar.addTab(tabB);

        Tab tabC = actionBar.newTab();
        tabC.setText("Tab C");
        tabC.setTabListener(new TabListener<ThisWeek>(this, "Tag C", ThisWeek.class));
        actionBar.addTab(tabC);

        Tab tabD = actionBar.newTab();
        tabC.setText("Tab D");
        tabC.setTabListener(new TabListener<Estore>(this, "Tag D", Estore.class));
        actionBar.addTab(tabD);


        if (savedInstanceState != null) {
            int savedIndex = savedInstanceState.getInt("SAVED_INDEX");
            getActionBar().setSelectedNavigationItem(savedIndex);
        }
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        // TODO Auto-generated method stub
        super.onSaveInstanceState(outState);
        outState.putInt("SAVED_INDEX", getActionBar().getSelectedNavigationIndex());
    }


    public static class TabListener<T extends Fragment> implements ActionBar.TabListener{
        private final Activity myActivity;
        private final String myTag;
        private final Class<T> myClass;


        public TabListener(Activity activity, String tag, Class<T> cls) {
            myActivity = activity;
            myTag = tag;
            myClass = cls;
        }

        @Override
        public void onTabSelected(Tab tab, FragmentTransaction ft) {

            Fragment myFragment = myActivity.getFragmentManager().findFragmentByTag(myTag);

           // Check if the fragment is already initialized
           if (myFragment == null) {
               // If not, instantiate and add it to the activity
               myFragment = Fragment.instantiate(myActivity, myClass.getName());
               ft.add(android.R.id.content, myFragment, myTag);
           } else {
               // If it exists, simply attach it in order to show it
               ft.attach(myFragment);
           }
        }

        @Override
        public void onTabUnselected(Tab tab, FragmentTransaction ft) {
            Fragment myFragment = myActivity.getFragmentManager().findFragmentByTag(myTag);
            if (myFragment != null) {
                // Detach the fragment, because another one is being attached
            ft.detach(myFragment);
            }
        }

        @Override
        public void onTabReselected(Tab tab, FragmentTransaction ft) {
            // TODO Auto-generated method stub
        }
    }
}

Answer 1

您将“this”（当前活动对象）设置为侦听器：

tabA.setTabListener(new TabListener<Categories>(this, "Tag A", Categories.class));

要成为一个监听器，活动应该实现适当的接口。所以：

以这种方式宣布您的活动：

    public class MainResource extends Activity implements TabListener

在activity中实现TabListener接口的方法（您的IDE将通过建议“实现方法......”来帮助您。）

您的代码可能存在更多问题，但您需要将正确的对象分配为TabListener。

Answer 2

Tab tabD = actionBar.newTab（）;

    tabC.setText("Tab D");

    tabC.setTabListener(new TabListener<Estore>(this, "Tag D", Estore.class));

将tabC更改为tabD，问题将解决。

操作栏选项卡必须具有回调

2 个答案: