设备进入待机状态后,如果我呼叫getSupportFragmentManager()
,则会得到一个FragmentManager
,其中包含未初始化且其所有变量都设置为null
的片段。
这里有一些代码:
this.mAdapter = new MyAdapter(getSupportFragmentManager());
this.mPager = (ViewPager) findViewById(R.id.pager);
this.mPager.setAdapter(mAdapter);
TabPageIndicator titleIndicator = (TabPageIndicator) findViewById(R.id.titles);
titleIndicator.setViewPager(mPager);
titleIndicator.setOnPageChangeListener(new OnPageChangeListener()
{
@Override
public void onPageSelected(int position)
{
mAdapter.getItem(position).onFocus();
}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2)
{
}
@Override
public void onPageScrollStateChanged(int arg0)
{
}
});
这是MyAdapter类:
public static class MyAdapter extends FragmentStatePagerAdapter
{
ArrayList<ExtendedFragment> tabs = new ArrayList<ExtendedFragment>();
String[] titles = new String[] { "FRAG1", "FRAG2", "FRAG3", "FRAG4", "FRAG5", "FRAG6"};
public MyAdapter(FragmentManager fm)
{
super(fm);
tabs.add(new frag1());
tabs.add(new frag2());
tabs.add(new frag3());
tabs.add(new frag4());
tabs.add(new frag5());
tabs.add(new frag6());
}
@Override
public int getCount()
{
return tabs.size();
}
@Override
public ExtendedFragment getItem(int position)
{
return tabs.get(position);
}
@Override
public CharSequence getPageTitle(int position)
{
return titles[position];
}
}
ExtendedFragment
实现方法onFocus()
,每个片段都覆盖该方法,因为当选项卡获得焦点时,我需要执行一些操作。当我从待机状态恢复设备并触发onFocus()
时,如果尝试使用View
获取getView()
,则会得到null
。为什么我的视图为空?
最佳答案
您可以尝试覆盖onSaveInstanceState方法。
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState != null) {
mContentFragment = getSupportFragmentManager().getFragment(
savedInstanceState, "mContent");
}
if (mContentFragment == null) {
mContentFragment = new YourFragment();
}
}
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
getSupportFragmentManager().putFragment(outState, "mContent",
mContentFragment);
}