[英]How do I use FragmentPagerAdapter to have tabs with different content?
I want to have different tabs, where you can swipe through like in the android market.我想要不同的标签,你可以像在 android 市场中那样滑动。 Each tab should use one fragment and use one method for it.
每个选项卡应使用一个片段并为其使用一种方法。
This is my FragmentPagerAdapter class:这是我的 FragmentPagerAdapter 类:
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
Fragment fragment =null;
switch (position) {
case 0:
fragment = new ConnectionFragment();
break;
case 1:
fragment = new DataFragment();
break;
case 2:
fragment = new GraphFragment();
break; }
return fragment;
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
}
And I have three classes for each fragment type/tab:我为每个片段类型/选项卡设置了三个类:
public static class ConnectionFragment extends Fragment {
public static final String ARG_SECTION_NUMBER = "section_number";
public String stringConnectionStatus = "Offline";
public String stringWiflyIp = "0.0.0.0";
public ConnectionFragment() {}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View connectionView = inflater.inflate(R.layout.fragment_connection,
container, false);
TextView statusView = (TextView) connectionView.findViewById(R.id.status_label);
statusView.setText("Connection status: " + stringConnectionStatus);
TextView ipView = (TextView) connectionView.findViewById(R.id.ip_label);
ipView.setText("WiFly IP: " + stringWiflyIp);
/**TextView sectionBarView = (TextView) connectionView
.findViewById(R.id.section_label);
sectionBarView.setText("pups");"*/
return connectionView;
}
}
public static class DataFragment extends Fragment {
public DataFragment() {}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View dataView = inflater.inflate(R.layout.fragment_data,
container, false);
TextView sectionBarView = (TextView) dataView
.findViewById(R.id.section_label);
sectionBarView.setText("pups2");
return dataView;
}
}
public static class GraphFragment extends Fragment {
public GraphFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_graph,
container, false);
TextView sectionBarView = (TextView) rootView
.findViewById(R.id.section_label);
sectionBarView.setText("pups3");
return rootView;
}
}
Each Fragment should be customizable, thats why I have three classes.每个 Fragment 都应该是可定制的,这就是为什么我有三个类。
Nevertheless, the app crashes in the getItem method.尽管如此,该应用程序还是会在 getItem 方法中崩溃。 Any ideas?
有任何想法吗? Thank you!
谢谢!
Edit: The complete MainActivity.java:编辑:完整的 MainActivity.java:
import ...
public class MainActivity extends FragmentActivity {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a
* {@link android.support.v4.app.FragmentPagerAdapter} derivative, which
* will keep every loaded fragment in memory. If this becomes too memory
* intensive, it may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
SectionsPagerAdapter mSectionsPagerAdapter;
public List<String> fragments = new Vector<String>();
/**
* The {@link ViewPager} that will host the section contents.
*/
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Create the adapter that will return a fragment for each of the three
// primary sections of the app.
mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager); //pager
mViewPager.setAdapter(mSectionsPagerAdapter);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
fragments.add(ConnectionFragment.class.getName());
fragments.add(DataFragment.class.getName());
fragments.add(GraphFragment.class.getName());
//fragmentsA = "fragments";
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a DummySectionFragment (defined as a static inner class
// below) with the page number as its lone argument.
/*Fragment fragment =null;
switch (position) {
case 0:
fragment = new ConnectionFragment();
break;
case 1:
fragment = new DataFragment();
break;
case 2:
fragment = new GraphFragment();
break; }
return fragment;*/
return Fragment.instantiate(getBaseContext(), fragments.get(position));
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
case 2:
return getString(R.string.title_section3).toUpperCase(l);
}
return null;
}
}
/**
* A dummy fragment representing a section of the app, but that simply
* displays dummy text.
*/
public static class ConnectionFragment extends Fragment {
/**
* The fragment argument representing the section number for this
* fragment.
*/
public static final String ARG_SECTION_NUMBER = "section_number";
public String stringConnectionStatus = "Offline";
public String stringWiflyIp = "0.0.0.0";
public ConnectionFragment() {}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View connectionView = inflater.inflate(R.layout.fragment_connection,container, false);
TextView statusView = (TextView) connectionView.findViewById(R.id.status_label);
statusView.setText("Connection status: " + stringConnectionStatus);
TextView ipView = (TextView) connectionView.findViewById(R.id.ip_label);
ipView.setText("WiFly IP: " + stringWiflyIp);
/**TextView sectionBarView = (TextView) connectionView
.findViewById(R.id.section_label);
sectionBarView.setText("pups");"*/
return connectionView;
}
}
public static class DataFragment extends Fragment {
public DataFragment() {}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View dataView = inflater.inflate(R.layout.fragment_data,
container, false);
//TextView sectionBarView = (TextView) dataView.findViewById(R.id.section_label);
//sectionBarView.setText("pups2");
return dataView;
}
}
public static class GraphFragment extends Fragment {
public GraphFragment() {}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_graph,
container, false);
//TextView sectionBarView = (TextView) rootView.findViewById(R.id.section_label);
//sectionBarView.setText("pups3");
return rootView;
}
}
}
Create the adapter:创建适配器:
class MyPagerAdapter extends FragmentPagerAdapter {
public List<String> fragmentsA;
public MyPagerAdapter(FragmentManager fm) {
super(fm);
fragmentsA = fragments;
}
@Override
public Fragment getItem(int position) {
//return MyFragment.newInstance();
return Fragment.instantiate(context, fragmentsA.get(position));
}
@Override
public CharSequence getPageTitle(int position) {
//return CONTENT[position % CONTENT.length].toUpperCase();
return mEntries.get(position % CONTENT.length).toUpperCase();
}
@Override
public int getCount() {
// return CONTENT.length;
return mEntries.size();
}
@Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
}
Each fragment belongs to different classes.每个片段属于不同的类。
So you have to define a fragment list (These go to the main FragmentActivity) :所以你必须定义一个片段列表(这些去主 FragmentActivity):
static MyPagerAdapter adapter;
and fill it with the fragments:并用碎片填充它:
fragments.add(ConnectionFragment.class.getName());
fragments.add(DataFragment.class.getName());
fragments.add(Tab3.class.getName());
//..etc
Then you have to add the fragments to the adapter like this:然后你必须像这样将片段添加到适配器:
pager = (ViewPager)findViewById(R.id.viewpager);
adapter = new MyPagerAdapter(getSupportFragmentManager());
pager.setAdapter(adapter);
The MyPagerAdaper will go through all the fragments contained by the fragments
list, then it will instantiate each of them. MyPagerAdaper 将遍历
fragments
列表中包含的所有片段,然后实例化它们中的每一个。
In your FragmentPagerAdapter#getItem method, do not create object of the Fragments.在您的 FragmentPagerAdapter#getItem 方法中,不要创建 Fragment 的对象。 You need to return the Fragment in the following way -
您需要通过以下方式返回 Fragment -
return Fragment.instantiate(context, ConnectionFragment.class.getName());
This means that the method will look like this -这意味着该方法将如下所示 -
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
Fragment fragment =null;
switch (position) {
case 0:
fragment = Fragment.instantiate(context, ConnectionFragment.class.getName());
break;
case 1:
fragment = Fragment.instantiate(context, DataFragment.class.getName());
break;
case 2:
fragment = Fragment.instantiate(context, GraphFragment.class.getName());
break; }
return fragment;
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
}
See this example:看这个例子:
public static class MyPagerAdapter extends FragmentPagerAdapter {
private static int NUM_ITEMS = 3;
public MyPagerAdapter(FragmentManager fragmentManager) {
super(fragmentManager);
}
// Returns total number of pages
@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: // Fragment # 0 - This will show FirstFragment
return FirstFragment.newInstance(0, "Page # 1");
case 1: // Fragment # 0 - This will show FirstFragment different title
return FirstFragment.newInstance(1, "Page # 2");
case 2: // Fragment # 1 - This will show SecondFragment
return SecondFragment.newInstance(2, "Page # 3");
default:
return null;
}
}
// Returns the page title for the top indicator
@Override
public CharSequence getPageTitle(int position) {
return "Page " + position;
}
}
With the release of ViewPager2 1.0.0 , the FragmentPagerAdapter
and FragmentStatePagerAdapter
classes for interacting with ViewPager
have been deprecated.随着ViewPager2 1.0.0的发布,用于与
ViewPager
交互的FragmentPagerAdapter
和FragmentStatePagerAdapter
类已被弃用。
ViewPager2
is an improved version of the ViewPager
library that offers enhanced functionality and addresses common difficulties with using ViewPager
. ViewPager2
是ViewPager
库的改进版本,它提供了增强的功能并解决了使用ViewPager
常见困难。
ViewPager2
ViewPager2
在片段之间实现滑动ViewPager2
ViewPager2
创建带有选项卡的滑动视图ViewPager
, read this page to learn more about migrating to ViewPager2
.ViewPager
,请 阅读此页面以了解有关迁移到ViewPager2
更多信息。
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