Android - 使用viewPager更新其他片段中的textview

时间:2013-11-16 05:16:22

标签: java android listview android-fragments

我正在尝试从片段中更新片段3中的textview,但它返回nullpointerexception。但是当我从片段1更新片段2(listview)时,它完美地工作。我想知道问题是什么,有人可以指导我吗?感谢。

我的片段2代码,我试图更新我的片段3:

public void onResume() {
    super.onResume();

    if (getListView() != null) {
        updateData();
        String tagName = "android:switcher:" + R.id.pager + ":" + 2;
        Bill f3 = (Bill)getActivity().getSupportFragmentManager().findFragmentByTag(tagName);
        f3.updateData2();
    }
}

我的片段3代码接收更新:

void updateData2() {
    EventController controller = new EventController(getActivity());
    Intent objIntent = getActivity().getIntent();
    String eventId = objIntent.getStringExtra("eventId");   
    total = (TextView) getActivity().findViewById(R.id.displaytotal);
    total.setText(controller.getTotal(eventId));
}

我的viewpager代码:

public class DashboardActivity2 extends FragmentActivity implements TabListener{

private ViewPager viewPager;
private TabsPagerAdapter2 mAdapter;
private ActionBar actionBar;
// Tab titles
    private String[] tabs = { "Participant", "Expense","Bill" };

    @SuppressLint("NewApi")
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        viewPager = (ViewPager) findViewById(R.id.pager);
        actionBar = getActionBar();
        mAdapter = new TabsPagerAdapter2(getSupportFragmentManager());

        viewPager.setAdapter(mAdapter);
        actionBar.setHomeButtonEnabled(false);
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        // Adding Tabs
        for (String tab_name : tabs) {
            actionBar.addTab(actionBar.newTab().setText(tab_name)
                    .setTabListener(this));
        }

        /**
         * on swiping the viewpager make respective tab selected
         * */
        viewPager
                .setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

                    @Override
                    public void onPageSelected(int position) {
                        // on changing the page
                        // make respected tab selected
                        actionBar.setSelectedNavigationItem(position);
                    }

                    @Override
                    public void onPageScrolled(int arg0, float arg1,
                            int arg2) {
                    }

                    @Override
                    public void onPageScrollStateChanged(int arg0) {
                    }
                });
    }

    @Override
    public void onTabReselected(Tab arg0, FragmentTransaction arg1) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onTabSelected(Tab arg0, FragmentTransaction arg1) {
        // TODO Auto-generated method stub
        // on tab selected
        // show respected fragment view
        viewPager.setCurrentItem(arg0.getPosition());
    }

    @Override
    public void onTabUnselected(Tab arg0, FragmentTransaction arg1) {
        // TODO Auto-generated method stub

    }
  }

这是我的LogCat:

11-16 05:46:08.912: E/AndroidRuntime(17241): FATAL EXCEPTION: main
11-16 05:46:08.912: E/AndroidRuntime(17241): java.lang.NullPointerException
11-16 05:46:08.912: E/AndroidRuntime(17241):    at com.example.hapshare.Expense.onResume(Expense.java:109)
11-16 05:46:08.912: E/AndroidRuntime(17241):    at android.support.v4.app.Fragment.performResume(Fragment.java:1521)
11-16 05:46:08.912: E/AndroidRuntime(17241):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:963)
11-16 05:46:08.912: E/AndroidRuntime(17241):    at android.support.v4.app.FragmentManagerImpl.performPendingDeferredStart(FragmentManager.java:823)
11-16 05:46:08.912: E/AndroidRuntime(17241):    at android.support.v4.app.FragmentManagerImpl.startPendingDeferredFragments(FragmentManager.java:1128)

1 个答案:

答案 0 :(得分:0)

我唯一能想到的是,当不可见时,片段可能会与活动分离。因此,在updateData2()中,您应该避免执行任何需要Activity的操作(如getActivity())。保存数据,在进入onResume()方法之前不要对其执行任何操作。

BTW,我发现onAttach()在onCreate()之前被调用。因此,您可以执行任何需要onCreate(),onCreateView()或onStart()以及onResume()中的Activity的内容。