Question

亲爱的，

我搜索了这个问题超过一天，但没有运气。我完全实现了这里发布的代码：

我的onTabSelected代码如下：

public void onTabSelected(Tab tab, FragmentTransaction ft) {
        // Check if the fragment is already initialized
        if (mFragment == null) {
            // If not, instantiate and add it to the activity
            mFragment = Fragment.instantiate(mActivity, mClass.getName());
            ft.add(R.id.alert_fragment_container, mFragment, mTag);
        } else {
            // If it exists, simply attach it in order to show it
            ft.attach(mFragment);
        }

        // prepare adapter for ExpandableListView

        Log.i("After Adapter Created", "Passed");

        final ExpandableListAdapter expListAdapter = new AlertsAdapter(
                mActivity, myAlerts, violations);

        Log.i("After Adapter Initialized", "Passed");

       ((MyCustomFragment)mFragment).violations.setAdapter(expListAdapter);
    }

代码工作正常，直到最后一行，我需要在MyCustomFragment中的onCreateView中初始化的公共静态列表设置适配器，这里是我的代码片段：

public class MyCustomFragment extends Fragment {

    public MyCustomFragment() {
    }

    public static ExpandableListView violations; 

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_alerts_poi, container, false);

        violations = (ExpandableListView) rootView.findViewById(R.id.POIAlertList);

        Log.i("onCreateView POI", "Called");

        return rootView;
    }
}

它给出Null指针错误。使用我的调试日志，我注意到此Log.i("onCreateView POI", "Called");后出现此日志Log.i("After Adapter Initialized", "Passed");。这意味着我正在尝试为片段设置适配器尚未初始化。

这是我面临的确切问题，我需要根据ExpandableListView中的标签选择向onTabSelected提供数据。

我做错了什么？什么是最好的解决方案？

此致

Answer 1

您似乎需要一个 ViewPager ，我刚刚在几天前实现了导航标签，这是我的代码，它在4个片段之间导航：

public class MainActivity extends FragmentActivity implements ActionBar.TabListener{
private ActionBar actionBar;
private ViewPager mViewPager;
private AppSectionsPagerAdapter mAppSectionsPagerAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());
    actionBar=getActionBar();
    actionBar.setHomeButtonEnabled(false);
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mAppSectionsPagerAdapter);
    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
        @Override
        public void onPageSelected(int position) {
            actionBar.setSelectedNavigationItem(position);
        }
    });
    actionBar.addTab(actionBar.newTab().setIcon(R.drawable.icon1).setTabListener(this));
    actionBar.addTab(actionBar.newTab().setIcon(R.drawable.icon2).setTabListener(this));
    actionBar.addTab(actionBar.newTab().setIcon(R.drawable.icon3).setTabListener(this));
    actionBar.addTab(actionBar.newTab().setIcon(R.drawable.icon4).setTabListener(this));     
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // TODO Auto-generated method stub
    getMenuInflater().inflate(R.menu.action_menu, menu);
    return true;
}

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

}

@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
    mViewPager.setCurrentItem(tab.getPosition());

}

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

}

这是适配器：

public class AppSectionsPagerAdapter extends FragmentPagerAdapter {
public AppSectionsPagerAdapter(FragmentManager fm) {
    super(fm);
}

@Override
public Fragment getItem(int i) {
    switch (i) {
        case 0:
            return new Fragment1();
        case 1:
            return new Fragment2();
        case 2:
            return new Fragment3();
        case 3: 
            return new Fragment4();
    }
    return null;
}

@Override
public int getCount() {
    return 4;
}

}

Answer 2

查看@ this Tablayout.onTabselected以获取最新的API更新。 ActionBar.TabListener是一个旧的实现。

在onTabSelected中播放片段

2 个答案: