安卓 Frament + ViewPager使用示例

1. 组成架构

• 整个架构被包在一个外部Fragment之中，也可以放在一个Activity之中，随意。
• 外部的fragment包含了两个组件，即途中的ViewPager和TabLayout
• ViewPager要套上一个FragmentStatePagerAdapter ，适配器负责new出一个个fragment，这些fragment object就是负责装数据的一个个页面。
• ViewPager可以和TabLayout进行关联

2. 实现步骤

2.1 创建内部的fragment object和外部的Fragment

public class ObjectFragment extends Fragment {private static String OBJ_INDEX = "objectIndex";private String mIndex;public ObjectFragment() {}public static ObjectFragment newInstance(String param1) {ObjectFragment fragment = new ObjectFragment();Bundle args = new Bundle();args.putString(OBJ_INDEX, param1);fragment.setArguments(args);return fragment;}@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);if (getArguments() != null) {mIndex = getArguments().getString(OBJ_INDEX);}}@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {return inflater.inflate(R.layout.fragment_object, container, false);}@Overridepublic void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {((TextView) view.findViewById(R.id.tv_frg_obj)).setText("item" + mIndex);}}

public class OuterFragment extends Fragment {public OuterFragment() {// Required empty public constructor}public static OuterFragment newInstance() {OuterFragment fragment = new OuterFragment();return fragment;}@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);}@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {// Inflate the layout for this fragmentreturn inflater.inflate(R.layout.fragment_outer, container, false);}
}

下面是OuterFragment的页面，由架构图可以看出，外部的fragment包含了ViewPager和TabLayout，但是在具体的页面中，TabLayout被放进了ViewPager中

    <androidx.viewpager.widget.ViewPagerandroid:id="@+id/pager"android:layout_width="match_parent"android:layout_height="match_parent"><com.google.android.material.tabs.TabLayoutandroid:id="@+id/tab_layout"android:layout_width="match_parent"android:layout_height="wrap_content" /></androidx.viewpager.widget.ViewPager>

2.2 创建FragmentStatePagerAdapter适配器

这个东西就是ViewPager的适配器

public class MyFragmentStatePagerAdapter extends FragmentStatePagerAdapter {public MyFragmentStatePagerAdapter(@NonNull FragmentManager fm) {super(fm);}@NonNull@Overridepublic Fragment getItem(int position) {Fragment fragment = ObjectFragment.newInstance(position + 1 + "");return fragment;}@Overridepublic int getCount() {return 10;}@Overridepublic CharSequence getPageTitle(int position) {return "" + (position + 1);}}

2.3 给ViewPager设置适配器

这里的步骤都在OuterFragment中操作

添加以下成员：

MyFragmentStatePagerAdapter fragmentStatePagerAdapter;
ViewPager viewPager;

在以下函数中进行设置：

    @Overridepublic void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {//设置ViewPager的适配器viewPager = view.findViewById(R.id.pager);fragmentStatePagerAdapter = new MyFragmentStatePagerAdapter(getChildFragmentManager());viewPager.setAdapter(fragmentStatePagerAdapter);//设置TabLayout与viewPager关联TabLayout tabLayout = view.findViewById(R.id.tab_layout);tabLayout.setupWithViewPager(viewPager);}

3. 启动

在MainActivity中添加外部的OuterFragment

3.1 布局文件中添加FrameLayout

<FrameLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"android:id="@+id/fr_container"android:orientation="horizontal">
</FrameLayout>

3.2 启动Fragment

public class MainActivity extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);OuterFragment outerFragment = new OuterFragment();FragmentManager manager = getSupportFragmentManager();FragmentTransaction transaction = manager.beginTransaction();transaction.add(R.id.fr_container, outerFragment,"1");transaction.addToBackStack(null);transaction.commit();}
}