FragmentPagerAdapter使用

最新推荐文章于 2024-08-13 19:41:47 发布

原创最新推荐文章于 2024-08-13 19:41:47 发布 · 532 阅读

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本文介绍了一个使用ViewPager和TabLayout实现页面切换功能的TabsActivity类。该类通过自定义FPAdapter适配器来管理多个Fragment，并实现了根据不同的Tab显示相应Fragment的功能。

public class TabsActivity extends AppCompatActivity {

    private FPAdapter adapter;
    private ViewPager mViewPager;
    private TabLayout tabLayout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.tab_layout);

        mViewPager = (ViewPager) findViewById(R.id.container);
        tabLayout = (TabLayout) findViewById(R.id.tabs);

        adapter = new FPAdapter(getSupportFragmentManager());
        mViewPager.setAdapter(adapter);
        tabLayout.setupWithViewPager(mViewPager);
    }

    /**
     * @Description: 自定义Fragment适合器，继承自FragmentPagerAdapter
     * @Author: Yong  QQ:281997672@qq.com
     * @Created at: 2017/3/3 15:20
     */
    Fragment[] fragments = {new Image1Fragment(), new Image2Fragment(), new Image3Fragment()};
    boolean[] fragmentsUpdateFlag = {false, false, false};

    public class FPAdapter extends FragmentPagerAdapter {
        FragmentManager fm;

        public FPAdapter(FragmentManager fm) {
            super(fm);
            this.fm = fm;
        }

        @Override
        public int getCount() {
            return fragments.length;
        }

        @Override
        public Fragment getItem(int position) {
            Fragment fragment = fragments[position % fragments.length];
            return fragment;
        }

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            //得到缓存的fragment
            Fragment fragment = (Fragment) super.instantiateItem(container, position);
            //得到tag，这点很重要
            String fragmentTag = fragment.getTag();
            //如果这个fragment需要更新
            if (fragmentsUpdateFlag[position % fragmentsUpdateFlag.length]) {
                FragmentTransaction ft = fm.beginTransaction();
                ft.remove(fragment);//移除旧的fragment
                fragment = fragments[position % fragments.length];//换成新的fragment
                ft.add(container.getId(), fragment, fragmentTag);//添加新fragment时必须用前面获得的tag，这点很重要
                ft.attach(fragment);
                ft.commit();
                fragmentsUpdateFlag[position % fragmentsUpdateFlag.length] = false;//复位更新标志
            }
            return fragment;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            super.destroyItem(container, position, object);
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return "SECTION 1";
                case 1:
                    return "SECTION 2";
                case 2:
                    return "SECTION 3";
                default:
                    return null;
            }
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <android.support.v4.view.ViewPager
        android:id="@+id/container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>