Question

我有以下结构

Activity 
   |________ Spinner
   |________ TabHost
                |_______ Fragment1
                             |________ LinearLayout
                |_______ Fragment2

当我在spinner中更改选项时，我应该在LinearLayout中添加（Fragment3 OR Fragment4 OR Fragment5）

我在微调器中使用的代码

spinner.setOnItemSelectedListener(new OnItemSelectedListener() {

                    @Override
                    public void onItemSelected(AdapterView<?> parent, View view,
                            int position, long id) {
                        Fragment1 fragment = (BaseFragment) mTabFragments.get(mTabHost.getCurrentTab());
                        fragment.updateCurrentFragment(position);
                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> arg0) {
                        // TODO Auto-generated method stub

                    }
                });

添加片段的代码

public void updateCurrentFragment (int index) {

    switch (index) {
    case 0:
        replaceFragment(new Fragment3());
        break;
    case 1:
        replaceFragment(new Fragment4());
        break;
    case 2:
        replaceFragment(new Fragment5());
        break;
    }
}

public void replaceFragment (Fragment newFragement) {

    FragmentTransaction transaction = getActivity().getSupportFragmentManager().beginTransaction();
    transaction.add(R.id.fragment_layout, newFragement);
    transaction.setCustomAnimations(android.R.anim.slide_in_left, android.R.anim.slide_out_right);
    transaction.commit();       
}

我现在得到空指针异常，并且getActivity = null

Answer 1

虽然你还没有共享整个类，但是看来updateCurrentFragment（）和replaceFragment（）函数已经在Interface BaseFragment中编写，或者在单独的Fragment1，Fragment2等文章中编写，如果我错了，请纠正我。在这种情况下，getActivity（）将始终返回null，因为尚未在当前活动中添加新的Fragment。因此，您可能需要将当前活动的实例（父活动）传递给BaseFragment，或者个人claees扩展BaseFragment，然后将该实例用于getActivity，如

（BaseFragment的实例）.getActivity（）而不仅仅是getActivity（）。

以下是您修改后的代码版本

spinner.setOnItemSelectedListener（new OnItemSelectedListener（）{

                @Override
                public void onItemSelected(AdapterView<?> parent, View view,
                        int position, long id) {
                    Fragment1 fragment = (BaseFragment) mTabFragments.get(mTabHost.getCurrentTab());
                    fragment.updateCurrentFragment(**this**,position);
                }

                @Override
                public void onNothingSelected(AdapterView<?> arg0) {
                    // TODO Auto-generated method stub

                }
            });

public void updateCurrentFragment（ParentActivity pAct ，int index）{

switch (index) {
case 0:
    replaceFragment(**pAct**,new Fragment3());
    break;
case 1:
    replaceFragment(**pAct**,new Fragment4());
    break;
case 2:
    replaceFragment(**pAct**,new Fragment5());
    break;
}

}

public void replaceFragment（（ParentActivity pAct ，Fragment newFragement）{

FragmentTransaction transaction = **pAct**.getActivity().getSupportFragmentManager().beginTransaction();
transaction.add(R.id.fragment_layout, newFragement);
transaction.setCustomAnimations(android.R.anim.slide_in_left, android.R.anim.slide_out_right);
transaction.commit();

}

如果这可以解决您的问题，请告诉我。

尝试在另一个片段内添加片段时为空指针

1 个答案: