二十八、Fragment + ViewPager使用

1. activity_main.xml

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

    <androidx.viewpager2.widget.ViewPager2
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:id="@+id/id_viewpager"
        android:background="@color/purple_200">
    </androidx.viewpager2.widget.ViewPager2>

</LinearLayout>

2. fragment_blank.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".BlankFragment">
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:textSize="36sp"
        android:id="@+id/text"
        android:gravity="center"
        android:text="测试" />
</FrameLayout>

3.  BlankFragment

package com.example.pagerrun;

import android.os.Bundle;

import androidx.fragment.app.Fragment;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class BlankFragment extends Fragment {
    private static final String ARG_TEXT = "param1";
    private String mTextString;
    View rootview;

    public BlankFragment() {
    }
    public static BlankFragment newInstance(String param1) {
        BlankFragment fragment = new BlankFragment();
        Bundle args = new Bundle();
        args.putString(ARG_TEXT, param1);
        fragment.setArguments(args);
        return fragment;
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mTextString = getArguments().getString(ARG_TEXT);
        }
    }
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        if (rootview == null){
            rootview = inflater.inflate(R.layout.fragment_blank, container, false);
        }
        initView();
        return rootview;
    }
    private void initView() {
        TextView textView = rootview.findViewById(R.id.text);
        String sa=mTextString;
        textView.setText(mTextString);
    }
}

4.  MyFragmentPagerAdapter

package com.example.pagerrun;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.lifecycle.Lifecycle;
import androidx.viewpager2.adapter.FragmentStateAdapter;

import java.util.ArrayList;
import java.util.List;

public class MyFragmentPagerAdapter extends FragmentStateAdapter {
    List<Fragment> fragmentList = new ArrayList<>();
    public MyFragmentPagerAdapter(@NonNull FragmentManager fragmentManager, @NonNull Lifecycle lifecycle,List<Fragment> fragments) {
        super(fragmentManager, lifecycle);
        fragmentList = fragments;
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        return fragmentList.get(position);
    }

    @Override
    public int getItemCount() {
        return fragmentList.size();
    }
}

5. MainActivity

package com.example.pagerrun;

import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.viewpager2.widget.ViewPager2;

import android.os.Bundle;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {
    ViewPager2 viewPager2;

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

    private void initPager() {

        viewPager2 = findViewById(R.id.id_viewpager);

        ArrayList<Fragment> fragments = new ArrayList<>();
        fragments.add(BlankFragment.newInstance("微信聊天"));
        fragments.add(BlankFragment.newInstance("通讯录"));
        fragments.add(BlankFragment.newInstance("发现"));
        fragments.add(BlankFragment.newInstance("我的"));

        MyFragmentPagerAdapter pagerAdapter = new MyFragmentPagerAdapter(getSupportFragmentManager(), getLifecycle(),fragments);
　　　　 

　　　　 viewPager2.setAdapter(pagerAdapter);
    }
}