NullPointerException: android.support.v4.app.FragmentHostCallback.getHandler()在空对象引用上。

I am facing following issue.

我正面临以下问题。

Scenario:

场景:

For the very first time when I signup thru app, I am able to see tabs and there content but when I logout and try to login for the same code for viewpager i get following exception:

我第一次通过app注册时，我可以看到标签和内容，但当我登出并尝试为viewpager登录相同的代码时，我遇到了以下例外:

NullPointerException: Attempt to invoke virtual method 'android.os.Handler android.support.v4.app.FragmentHostCallback.getHandler()' on a null object reference

NullPointerException:尝试调用虚拟方法的android.os。处理器android.support.v4.app.FragmentHostCallback.getHandler()'在空对象引用上。

but when open navigation menu and select after that I get data and tabs are shown viewpager shows tabs.

但是当打开导航菜单并选择之后，我得到了数据，标签显示了viewpager显示了标签。

Contents: I have 2 tabs

内容:我有两个标签。

Below is my code:

下面是我的代码:

 public void setupDashboardTabs(List<CreateFragmentsPojo> fragments) {
    this.fragments = fragments;

    viewPager = (ViewPager) findViewById(R.id.viewpager); 
    viewPager.setOffscreenPageLimit(3);

    setupDashboardViewPager(fragments);

    tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(viewPager);

    setUpFontStyleForTabs();
}


public void setupDashboardViewPager(List<CreateFragmentsPojo> fragments) {
    try {
        ViewPagerAdapter adapter = new ViewPagerAdapter(getSupportFragmentManager());

        for (int i = 0; i < fragments.size(); i++) {
            adapter.addFragment(fragments.get(i).getFragment(), fragments.get(i).getTitle());
        }
        viewPager.setAdapter(adapter);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

viewPager.setAdapter(adapter); getting nullpointer execption at this line

viewPager.setAdapter(适配器);在这一行获取nullpointer执行

Code to logout:

代码注销:

 Intent intent = new Intent(this, LoginActivity.class);
    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP | Intent.FLAG_ACTIVITY_NEW_TASK);
    startActivity(intent);
    finish();

Stacktrace:

加:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.os.Handler android.support.v4.app.FragmentHostCallback.getHandler()' on a null object reference
 W/System.err:     at android.support.v4.app.FragmentManagerImpl.ensureExecReady(FragmentManager.java:1949)
 W/System.err:     at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1965)
 W/System.err:     at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:620)
 W/System.err:     at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:166)
 W/System.err:     at android.support.v4.view.ViewPager.setAdapter(ViewPager.java:513)
 W/System.err:     at io.skreem.dashboard.DashboardActivity.setupDashboardViewPager(DashboardActivity.java:459)
 W/System.err:     at io.skreem.dashboard.DashboardActivity.setupDashboardTabs(DashboardActivity.java:443)
 W/System.err:     at io.skreem.dashboard.DashboardActivity$4.onResponse(DashboardActivity.java:408)
 W/System.err:     at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall$1$1.run(ExecutorCallAdapterFactory.java:68)
 W/System.err:     at android.os.Handler.handleCallback(Handler.java:746)
 W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:95)
 W/System.err:     at android.os.Looper.loop(Looper.java:148)
 W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:5443)
 W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
 W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
 W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)

2 个解决方案

#1

viewPager.setOffscreenPageLimit(3);

is the problem. As you have 2 tabs. Which means 2 pages but you are forcing 3 as the PageLimit. Also whats the need of adding fragment to adapter?

是这个问题。因为你有两个标签。这意味着2页，但你强迫3页作为页面限制。还需要向适配器添加片段吗?

2 个解决方案

#1

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