闲来无事记录一下TabLayout+ViewPager或ViewPager2的用法

一、初始化所需控件

	// 3个控件
  	private lateinit var mTabLayout: TabLayout
    private lateinit var mViewPager: ViewPager
    private lateinit var mViewPager2: ViewPager2
	
	// 两个List
    private val mTitle: MutableList<String> = ArrayList()
    private val mFragment: MutableList<Fragment> = ArrayList()
    
    ...
    	// 绑定并初始化数据
        mTabLayout = findViewById(R.id.layouts)
        mViewPager = findViewById(R.id.viewpager1)
        mViewPager2 = findViewById(R.id.viewpager2)
         for (i in 0..7) {
            mTitle.add("1==$i")
            mFragment.add(MyFragment())
        }

二、TabLayout+ViewPager

        mViewPager.offscreenPageLimit = mFragment.size
        mViewPager.adapter = object : FragmentPagerAdapter(supportFragmentManager) {
            override fun getItem(position: Int): Fragment {
                return mFragment[position]
            }

            override fun getCount(): Int {
                return mFragment.size
            }

            override fun getPageTitle(position: Int): CharSequence {
                return mTitle[position]
            }
        }
        mTabLayout.setupWithViewPager(mViewPager)

三、TabLayout+ViewPager2

// viewpager2
        mViewPager2.offscreenPageLimit = mFragment.size
        mViewPager2.adapter = object :
            FragmentStateAdapter(supportFragmentManager, this.lifecycle) {
            override fun createFragment(position: Int): Fragment {
                return mFragment[position]
            }

            override fun getItemCount(): Int {
                return mFragment.size
            }
        }

        TabLayoutMediator(
            mTabLayout,
            mViewPager2
        ) { tab: TabLayout.Tab, position: Int ->
            tab.text = mTitle[position]
        }.attach()

MyFragment

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

public class MyFragment extends Fragment {
   @Nullable
   @Override
   public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
       return inflater.inflate(R.layout.layout1,null);
   }
}

相对简易,没必要放全代码了,自记录。

Android中,通常使用`FragmentTransaction`和`FragmentManager`配合`FragmentPagerAdapter`来实现顶部导航的功能,特别是当应用需要支持多种布局结构,而每个布局对应不同的页面内容时。这里是一个简化的示例: ```java // 首先,定义顶部导航栏(FragmentPagerAdapter) public class NavAdapter extends FragmentPagerAdapter { private final List<Fragment> mFragments = new ArrayList<>(); // 添加你的Fragment实例到列表 public NavAdapter(FragmentManager fm) { super(fm); } @Override public Fragment getItem(int position) { return mFragments.get(position); } @Override public int getCount() { return mFragments.size(); } } // 在Activity中设置Fragment栈和顶部导航 private NavAdapter navAdapter; private ViewPager viewPager; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); navAdapter = new NavAdapter(getSupportFragmentManager()); viewPager = findViewById(R.id.view_pager); viewPager.setAdapter(navAdapter); // 顶部导航栏设置 setupViewPager(viewPager); // 自定义的方法,用于初始化ViewPager的内容 TabLayout tabLayout = findViewById(R.id.tab_layout); tabLayout.setupWithViewPager(viewPager); } private void setupViewPager(ViewPager viewPager) { // 分别创建并添加各个Fragment Fragment fragment1 = new Fragment1(); // 替换为实际的Fragment Fragment fragment2 = new Fragment2(); // 等等... mFragments.add(fragment1); mFragments.add(fragment2); // 当切换顶部导航时,更新对应的Fragment viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout)); tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() { @Override public void onTabSelected(TabLayout.Tab tab) { viewPager.setCurrentItem(tab.getPosition(), true); } @Override public void onTabUnselected(TabLayout.Tab tab) { // 当其他tab被选择时,隐藏当前显示的fragment if (viewPager.getCurrentItem() == tab.getPosition()) { FragmentManager fragmentManager = getSupportFragmentManager(); fragmentManager.popBackStackImmediate(); } } @Override public void onTabReselected(TabLayout.Tab tab) {} }); } ```
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