我使用ViewPager和3个片段编写了一个程序。我的问题是:
创建活动时,首先调用2个片段。从片段1到2时,单击或滚动片段2时,将调用片段3的onCreateView()
方法。并且,当我从片段3向后移动到片段2到片段1时,public class ViewPagerAdapter extends FragmentPagerAdapter {
private static int NUM_ITEMS = 3;
Context context;
public ViewPagerAdapter(FragmentManager manager,Context context) {
super(manager);
this.context = context;
}
@Override
public int getCount() {
return NUM_ITEMS;
}
// Returns the fragment to display for that page
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return Fragment_About.newInstance("About",20);
case 1:
return Fragment_EditSkills.newInstance ("Skills",30);
case 2:
return Fragment_EditActivities.newInstance("Activities",40);
default:
return null;
}
}
}
方法被调用。
我的代码:
ViewPagerAdapter.java
public class Fragment_About extends Fragment {
public static Fragment_About newInstance(String name, int age) {
Bundle bundle = new Bundle();
bundle.putString("name", name);
bundle.putInt("age", age);
Fragment_About fragment = new Fragment_About();
fragment.setArguments(bundle);
Log.i("FragmentAbout instance","instance");
Log.i("name",""+name);
Log.i("age",""+age);
return fragment;
}
private void readBundle(Bundle bundle) {
if (bundle != null) {
name = bundle.getString("name");
age = bundle.getInt("age");
Log.i("readBundle oncreateview","readBundle oncreateview");
Log.i("name",""+name);
Log.i("age",""+age);
}
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup
container, @Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_about, container,
false);
txtEditAbout = (TextView) view.findViewById(R.id.textEditAbout);
about = (TextView) view.findViewById(R.id.about);
readBundle(getArguments());
}
}
Fragment_About.java
// when the activity is created.
I/FragmentAbout instance: instance
I/EditSkills instance: instance
// When I click on page 2
I/FragActivity instance: instance
日志:
newInstance()
从3向后移动到片段2到片段1被调用,但这次没有为任何片段调用I/readBundle oncreateview: readBundle oncreateview
System.out.printf("The Sum is %d%n" , sum);
请解释上述过程。
答案 0 :(得分:0)
Viewpager根据 OffscreenPageLimit 参数预加载邻居片段。默认情况下,它设置为1( DEFAULT_OFFSCREEN_PAGES = 1)
您使用了 FragmentPagerAdapter ,这意味着如果片段视图远离屏幕外限制,则可以销毁它。