ViewPager2+Fragment+TabLayout

标签：Fragment private HomeFragment ViewPager2 import android TabLayout

ViewPager2

2019初Google正式发布了ViewPager2。只要我们已经从Suppor库切换到AndroidX，便可以使用ViewPager2完全取代旧的ViewPager。

ViewPager2最显著的特点是基于RecyclerView实现，RecyclerView是目前Android端最成熟的AdapterView解决方案，这带来诸多好处：

• 抛弃传统的PagerAdapter，统一了Adapter的API
• 通过LinearLayoutManager可以实现类似抖音的纵向滑动
• 支持DiffUitl，可以通过diff实现局部刷新
• 支持RTL（right-to-left）布局，对于一些有出海需求的APP非常有用
• 支持ItemDecorator

ViewPager2 + Fragment

跟ViewPager一样，除了View以外，ViewPager2更多的是配合Fragment的使用，这需要借助FragmentStateAdapter：

View	Adapter
ViewPager	FragmentStatePagerAdapter、PagerAdapter
ViewPager2	FragmentStateAdapter

 

TabLayout

 TabLayout提供了一个水平布局用于展示tabs，继承自HorizontalScrollView。

一般与Viewpager结合使用实现页面和标签联动的效果，是时下APP中非常常用的一个控件。

1、简单应用（两种方式）

（1）xml中添加tab

<android.support.design.widget.TabLayout
    android:id="@+id/tab_layout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <android.support.design.widget.TabItem
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tab1"/>
    <android.support.design.widget.TabItem
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tab2"/>
    <android.support.design.widget.TabItem
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tab3"/>
    <android.support.design.widget.TabItem
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Tab4"/>
</android.support.design.widget.TabLayout>

（2）代码中添加tab

xml文件

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

java代码

// tablayout，Tab是TabLayout的内部类，且Tab的构造方法是包访问权限
TabLayout tabLayout = (TabLayout) findViewById(R.id.tab_layout);
tabLayout.addTab(tabLayout.newTab().setText("Tab1"));
tabLayout.addTab(tabLayout.newTab().setText("Tab2"));
tabLayout.addTab(tabLayout.newTab().setText("Tab3"));
tabLayout.addTab(tabLayout.newTab().setText("Tab4"));

 2、TabLayout属性详解

<declare-styleable name="TabLayout">
    <!--指示器颜色-->
    <attr name="tabIndicatorColor" format="color"/>
    <!--指示器高度-->
    <attr name="tabIndicatorHeight" format="dimension"/>
     <!--指示器宽度 true:和tab同宽  false：和tab中的字同宽 -->
    <attr name="tabIndicatorFullWidth" format="boolean"/>
    <!--tabs距TabLayout开始位置的偏移量，但app:tabMode="scrollable"才生效-->
    <attr name="tabContentStart" format="dimension"/>
    <!--仅是Tab背景，设置TabLayout背景用android:background-->
    <attr name="tabBackground" format="reference"/>
    <!--默认fixed，所有Tab只能在屏幕内显示，超出会被挤压；scrollable,tab数量多会超出屏幕，可滑动-->
    <attr name="tabMode">
        <enum name="scrollable" value="0"/>
        <enum name="fixed" value="1"/>
    </attr>
    <!--默认fill，tab填满TabLayout,但tabMode=“fixed”才生效；center，tabs位于TabLayout的中间-->
    <attr name="tabGravity">
        <enum name="fill" value="0"/>
        <enum name="center" value="1"/>
    </attr>
    <!--Tab的最小宽度-->
    <attr name="tabMinWidth" format="dimension"/>
    <!--Tab的最大宽度-->
    <attr name="tabMaxWidth" format="dimension"/>
    <!--Tab文本设置样式-->
    <attr name="tabTextAppearance" format="reference"/>
    <!--Tab未选中字体颜色-->
    <attr name="tabTextColor" format="color"/>
    <!--Tab选中字体颜色-->
    <attr name="tabSelectedTextColor" format="color"/>
    <!--Tab内填充相关-->
    <attr name="tabPaddingStart" format="dimension"/>
    <attr name="tabPaddingTop" format="dimension"/>
    <attr name="tabPaddingEnd" format="dimension"/>
    <attr name="tabPaddingBottom" format="dimension"/>
    <attr name="tabPadding" format="dimension"/>
</declare-styleable>

使用示例

 <android.support.design.widget.TabLayout
    android:id="@+id/tab_layout"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:tabIndicatorColor="@color/colorPrimaryDark"
    app:tabIndicatorHeight="2dp"
    app:tabContentStart="50dp"
    app:tabBackground="@color/colorAccent"
    app:tabMode="scrollable"
    app:tabGravity="fill"
    app:tabTextAppearance="@style/MyTabTextAppearance"
    app:tabTextColor="@android:color/black"
    app:tabSelectedTextColor="@android:color/white"/>

<style name="MyTabTextAppearance" parent="TextAppearance.Design.Tab">
    <item name="textAllCaps">false</item>
    <item name="android:textSize">18sp</item>
</style>

 

实践

1、创建MainActivity

MainActivity.java

package com.sdbi.smartcityli01;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
import androidx.viewpager2.adapter.FragmentStateAdapter;
import androidx.viewpager2.widget.ViewPager2;

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import com.google.android.material.tabs.TabLayout;
import com.google.android.material.tabs.TabLayoutMediator;
import com.sdbi.smartcityli01.fragment.HomeFragment;

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

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";
    private String[] menus = {"首页", "服务", "党建", "新闻", "个人"};
    private int[] menuLogos = {R.drawable.one, R.drawable.one, R.drawable.one, R.drawable.one, R.drawable.one};

    private List<Fragment> fragmentList;
    private ViewPager2 vpMain;
    private TabLayout tlMain;
//    private TabLayout.Tab tab;

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

        initView(); // 初始化控件

        fragmentList = new ArrayList<Fragment>();
        fragmentList.add(new HomeFragment());
        fragmentList.add(new HomeFragment());
        fragmentList.add(new HomeFragment());
        fragmentList.add(new HomeFragment());
        fragmentList.add(new HomeFragment());

        // 创建ViewPager2所使用的适配器，FragmentStateAdapter抽象类的实现类对象
        FragmentStateAdapter adapter = new FragmentStateAdapter(MainActivity.this) {
            @NonNull
            @Override
            public Fragment createFragment(int position) {
                return fragmentList.get(position);
            }

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

        vpMain.setAdapter(adapter); // 给ViewPager2设置适配器

        new TabLayoutMediator(tlMain, vpMain, (tab, position) -> { // TabLayout和ViewPager2关联到一起
//            tab.setText(menus[position]); // 设置Tab的标题
            tab.setCustomView(tabMenu(menuLogos[position], menus[position])); // 设置Tab的图标和标题
        }).attach();

//        for (int i = 0; i < menus.length; i++) { // 设置Tab的图标和标题
//            tab = tlMain.getTabAt(i);
//            tab.setCustomView(tabMenu(menuLogos[i], menus[i]));
//        }
    }

    private void initView() {
        vpMain = (ViewPager2) findViewById(R.id.vpMain);
        tlMain = (TabLayout) findViewById(R.id.tlMain);
    }

    private View tabMenu(int image, String title) {
        ImageView ivMenu;
        TextView tvMenu;
        View view = LayoutInflater.from(this).inflate(R.layout.tabmenu, null);
        ivMenu = (ImageView) view.findViewById(R.id.ivMenu);
        tvMenu = (TextView) view.findViewById(R.id.tvMenu);
        tvMenu.setText(title);
        ivMenu.setImageResource(image);
        return view;
    }
}

其中<ImageView>控件中显示图标，可以使用数组的形式存储图标资源，这里用5个一样的图标表示。

private int[] imageInt = {R.drawable.one, R.drawable.one, R.drawable.one, R.drawable.one, R.drawable.one};

home.png和homes.png

    

 布局文件activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    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:id="@+id/vpMain"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

    <com.google.android.material.tabs.TabLayout
        android:id="@+id/tlMain"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="0.1"
        android:background="@color/blue"
        app:tabIndicatorColor="@color/white"
        app:tabIndicatorHeight="3dp" />

</LinearLayout>

2、TabLayout的项目布局文件tabmenu.xml

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

    <ImageView
        android:id="@+id/ivMenu"
        android:layout_width="match_parent"
        android:layout_height="30dp" />

    <TextView
        android:id="@+id/tvMenu"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="App Title"
        android:textColor="@color/white"
        android:textSize="12sp" />

</LinearLayout>

3、每个子项目的图表资源one.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/homes" android:state_enabled="true" android:state_selected="true" />
    <item android:drawable="@drawable/home" />
</selector>

4、Android Studio向导创建空白的Fragment

HomeFragment.java

package com.sdbi.smartcityli01.fragment;

import android.os.Bundle;

import androidx.fragment.app.Fragment;

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

import com.sdbi.smartcityli01.R;

public class HomeFragment extends Fragment {
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    public HomeFragment() {
        // Required empty public constructor
    }

    // TODO: Rename and change types and number of parameters
    public static HomeFragment newInstance(String param1, String param2) {
        HomeFragment fragment = new HomeFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_home, container, false);
    }
}

布局文件fragment_home.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=".fragment.HomeFragment">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/hello_blank_fragment" />

</FrameLayout>

运行效果

 

标签：Fragment,private,HomeFragment,ViewPager2,import,android,TabLayout
From： https://www.cnblogs.com/lihuawei/p/16642947.html