我在我的FragmentActivity中使用dispatchKeyEvent並調用我的片段方法之一。以下是我使用我的FragmentActivity代碼:爲什麼當我從FragmentActivity調用Fragment的方法時ProgressBar變爲空?
public class ViewPagerFragment extends FragmentActivity{
MyAdapter mAdapter;
ViewPager mPager;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.viewpager_layout);
mAdapter = new MyAdapter(getSupportFragmentManager());
mPager = (ViewPager) findViewById(R.id.pager);
mPager.setAdapter(mAdapter);
mPager.setCurrentItem(0);
}
public void onResume() {
super.onResume();
}
public void onPause() {
super.onPause();
}
public void onDestroy() {
super.onDestroy();
}
@Override
public boolean dispatchKeyEvent(KeyEvent event) {
if(event.getKeyCode() == 66){
FragmentPagerAdapter fragmentPagerAdapter = (FragmentPagerAdapter) mPager.getAdapter();
((SecondFragment)fragmentPagerAdapter.getItem(1)).myOnKeyDown(input_str);
}
return super.dispatchKeyEvent(event);
}
public void onNewIntent(Intent intent) {
super.onNewIntent(getIntent());
}
public static class MyAdapter extends FragmentPagerAdapter {
public MyAdapter(FragmentManager fm) {
super(fm);
}
@Override
public int getCount() {
return 2;
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new FirstFragment();
case 1:
return new SecondFragment();
default:
return null;
}
}
}
}
以下是我的SecondFragment代碼。
public class SecondFragment extends Fragment{
ProgressBar spinner;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
public void onResume(){
super.onResume();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.secondfragment_layout, container, false);
spinner = (ProgressBar) view.findViewById(R.id.spinner);
return view;
}
public void myOnKeyDown(String barcode){
// following line gives NullPointerException
spinner.setVisibility(ProgressBar.VISIBLE);
}
}
在我SecondFragment的onCreateView我已經初始化的進度是在SecondFrament佈局文件。但是當我在我的FragmentActivity中從dispatchKeyEvent調用myOnKeyDown時,它總是變爲空。爲何如此,我該如何解決?提前致謝。
我想你需要添加更多的上下文來幫助診斷這個問題。這聽起來像你有兩個片段的活動,但沒有更多的上下文(和更多的代碼),很難提供任何幫助。 – Phil
我已添加代碼。請看一看。 – Piscean