简单易懂，一步一步带你灵活运用ViewPager

本文主要是介绍简单易懂，一步一步带你灵活运用ViewPager，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

ViewPager概念

ViewPager是google SDK V4包中自带的一个视图类。主要作用:可以用来实现多个屏幕间的切换。

常用方法介绍

1.setAdapter(PagerAdapter adapter)

设置一个PagerAdapter,它将根据需要为这个页面提供视图

2.setCurrentItem(int item)

设置当前选定页面。如果viewPager已经通过它的当前设配器完成了它的第一个布局，那么当前item和指定item之间将会有一个平滑的动画过滤。

3.setOffscreenPageLimit(int limit)

在空闲状态下，在视图次结果中，设置应该保留到当前页面两侧的页面数量。超过这个限制的页面将要在需要时从适配器中重新创建。

4.addOnPageChangeListener(ViewPager.OnPageChangeListener listener)

增加一个监听器，每当页面发生变化或者不断的滑动时，都会被调用。

5.removeOnPageChangeListener(ViewPager.OnPageChangeListener listener)

删除之前通过addOnPageChangeListener(OnPageChangeListener)添加的监听器。

ViewPager入门实例讲解（每行代码都有注释，看着注释基本会懂意思。）

实现步骤:

1.在主布局文件里加入VierPager控件

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="fill_parent"android:layout_height="fill_parent" ><android.support.v4.view.ViewPagerandroid:id="@+id/viewPager"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_gravity="center" /></RelativeLayout>

2.新建三个布局文件，用来滑动切换视图

layout1.xml

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

layout2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent"android:background="#ffff00"></LinearLayout>

layout3.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent"android:background="#ff00ff"></LinearLayout>

3.Java代码实现

public class ViewPagerActivity extends AppCompatActivity {private  ViewPager viewPager;     //对应的ViewPager控件private  View view1,view2,view3;  //对应的三个Viewprivate  List<View> viewList;     //View数组@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_view_pager);initView();initData();}/*** 初始化控件*/private void initView() {viewPager = findViewById(R.id.viewPager);LayoutInflater inflater=getLayoutInflater();view1=inflater.inflate(R.layout.layout1,null);view2=inflater.inflate(R.layout.layout2,null);view3=inflater.inflate(R.layout.layout3,null);}/*** 设置数据*/private void initData() {//添加三个布局文件viewList=new ArrayList<>();viewList.add(view1);viewList.add(view2);viewList.add(view3);//设置适配器viewPager.setAdapter(pagerAdapter);}//初始化PagerAdapter设配器PagerAdapter pagerAdapter=new PagerAdapter(){//返回要滑动的View的个数@Overridepublic int getCount() {return viewList.size();}//判断当前的View是否是instantiateItem添加的View@Overridepublic boolean isViewFromObject(@NonNull View view, @NonNull Object object) {return view==object;}//从当前container中删除指定位置（position）的View;@Overridepublic void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {container.removeView(viewList.get(position));}//第一：将当前视图添加到container中，第二：返回当前View@NonNull@Overridepublic Object instantiateItem(@NonNull ViewGroup container, int position) {container.addView(viewList.get(position));return viewList.get(position);}};
}

ViewPager进阶实例讲解

注：这是在入门实例基础上进阶的实例（使用Fragment实现ViewPager滑动页面）。

实现步骤:

实现设配器(FragmentPagerAdapter 或者 FragmentStatePagerAdapter)

注：FragmentPagerAdapter 和 FragmentStatePagerAdapter都是PagerAdapter的子类。主要的区别：FragmentStatePagerAdapter处理大量的页面切换，而FragmentPagerAdapter处理有限个静态Fragment页面。我们这里就使用FragmentStatePagerAdapter做讲解。

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import java.util.List;public class FragAdapter extends FragmentStatePagerAdapter {private List<Fragment> mFragments;//Fragment数组，用于保存用于滑动的Fragment对象public FragAdapter(FragmentManager fm,List<Fragment> fragments) {super(fm);mFragments=fragments;}//返回指定位置关联的Fragment@Overridepublic Fragment getItem(int position) {return mFragments.get(position);}//返回用于滑动的Fragment总数@Overridepublic int getCount() {return mFragments.size();}
}

新建三个fragment类

2.1第一个Fragment

XML(layout1.xml)

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

JAVA代码

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.example.lenovo.androidtest.R;public class Fragment1 extends Fragment {@Nullable@Overridepublic View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {return inflater.inflate(R.layout.layout1, container, false);}
}

2.2第二个Fragment

XML(layout2.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent"android:background="#ffff00"></LinearLayout>

JAVA代码

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;import com.example.lenovo.androidtest.R;public class Fragment2 extends Fragment {@Nullable@Overridepublic View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {return inflater.inflate(R.layout.layout2, container, false);}
}

2.3第三个Fragment

XML(layout3.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:orientation="vertical"android:layout_width="match_parent"android:layout_height="match_parent"android:background="#ff00ff"></LinearLayout>

JAVA代码

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;import com.example.lenovo.androidtest.R;public class Fragment3 extends Fragment {@Nullable@Overridepublic View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {return inflater.inflate(R.layout.layout3, container, false);}
}

注:其实大家发现没有，相对于入门级的布局文件，只是多了三个Fragment类来加载三个页面。

Activity代码实现

import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;import com.example.lenovo.androidtest.R;
import com.example.lenovo.androidtest.adapter.FragAdapter;
import com.example.lenovo.androidtest.fragment.Fragment1;
import com.example.lenovo.androidtest.fragment.Fragment2;
import com.example.lenovo.androidtest.fragment.Fragment3;import java.util.ArrayList;
import java.util.List;public class ViewPagerFragmentActivity extends AppCompatActivity {ViewPager vp;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_view_pager_fragment);initView();initData();}private void initView() {vp = findViewById(R.id.all_viewPage); //获取viewpage控件}private void initData() {List<Fragment> fragments=new ArrayList<>(); //构建一个Fragment列表//将三个Fragment实例添加到List中fragments.add(new Fragment1());  fragments.add(new Fragment2());fragments.add(new Fragment3());//生成一个FragAdapter实例FragAdapter adapter = new FragAdapter(getSupportFragmentManager(), fragments);//设定适配器vp.setAdapter(adapter);}
}

总结：其实进阶的实例只是在入门实例上用Fragment实现了同样的效果。上面的实例注意了，一定要导入V4包里面的Fragment。不然的话，List添加实例的时候会提示“无法将Fragment()转换为fragment”。

ViewPager应用(ViewPager+Fragment+TabLayout+RecyclerView)

注:现在就是带你实现平时我们开发中用得最多的黄金搭配了。ViewPager+Fragment+TabLayout+RecyclerView最强组合。

实现步骤:

1.1.新建Fragment布局文件（fragment_item_list）

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.RecyclerView 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:id="@+id/list"android:name="com.example.lenovo.androidtest.fragment.ItemFragment"android:layout_width="match_parent"android:layout_height="match_parent"android:layout_marginLeft="16dp"android:layout_marginRight="16dp"app:layoutManager="LinearLayoutManager"tools:context=".fragment.ItemFragment"tools:listitem="@layout/fragment_item" />

1.2新建Fragment类（ItemFragment）

import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.example.lenovo.androidtest.R;
import com.example.lenovo.androidtest.fragment.dummy.DummyContent;public class ItemFragment extends Fragment {// 对应页面标识名称private static final String ARG_COLUMN_COUNT = "column-count";// 对应页面标识private int mColumnCount = 1;public ItemFragment() {}//实例化ItemFragment,并且传入标识参数@SuppressWarnings("unused")public static ItemFragment newInstance(int columnCount) {ItemFragment fragment = new ItemFragment();Bundle args = new Bundle();args.putInt(ARG_COLUMN_COUNT, columnCount);fragment.setArguments(args);return fragment;}@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);if (getArguments() != null) {mColumnCount = getArguments().getInt(ARG_COLUMN_COUNT);//获取标识参数}}@Overridepublic View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {View view = inflater.inflate(R.layout.fragment_item_list, container, false);if (view instanceof RecyclerView) { //判断是否是RecyclerView控件Context context = view.getContext();RecyclerView recyclerView = (RecyclerView) view;//如果参数值小于等于1，就设置为线型列表，否则就是设置表格列表if (mColumnCount <= 1) {recyclerView.setLayoutManager(new LinearLayoutManager(context));} else {recyclerView.setLayoutManager(new GridLayoutManager(context, mColumnCount));}//设置列表设配器recyclerView.setAdapter(new MyItemRecyclerViewAdapter(DummyContent.ITEMS));}return view;}
}

2.1添加RecyclerView适配器（布局文件我就不写了）

import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import com.example.lenovo.androidtest.R;
import com.example.lenovo.androidtest.fragment.dummy.DummyContent.DummyItem;
import java.util.List;public class MyItemRecyclerViewAdapter extends RecyclerView.Adapter<MyItemRecyclerViewAdapter.ViewHolder> {private final List<DummyItem> mValues;public MyItemRecyclerViewAdapter(List<DummyItem> items) {mValues = items;}@Overridepublic ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fragment_item, parent, false);return new ViewHolder(view);}@Overridepublic void onBindViewHolder(final ViewHolder holder, int position) {holder.mItem = mValues.get(position);holder.mIdView.setText(mValues.get(position).id);holder.mContentView.setText(mValues.get(position).content);}@Overridepublic int getItemCount() {return mValues.size();}public class ViewHolder extends RecyclerView.ViewHolder {public final View mView;public final TextView mIdView;public final TextView mContentView;public DummyItem mItem;public ViewHolder(View view) {super(view);mView = view;mIdView = (TextView) view.findViewById(R.id.item_number);mContentView = (TextView) view.findViewById(R.id.content);}@Overridepublic String toString() {return super.toString() + " '" + mContentView.getText() + "'";}}
}

3.1Activity核心代码

import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import com.example.lenovo.androidtest.R;
import com.example.lenovo.androidtest.common.TabFragmentIndex;
import com.example.lenovo.androidtest.fragment.FragmentAdapter;
import com.example.lenovo.androidtest.fragment.ItemFragment;
import java.util.ArrayList;
import java.util.List;public class NewParentActivity extends AppCompatActivity{private ViewPager mViewpager;                               //ViewPager控件private TabLayout mTabLayout;                               //TabLayout控件private String[] tabs = new String[]{"首页","推荐","热点"}; //标题要显示的文字protected List<Fragment> fragments;                         //Fragment的List集合@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.test);initView();initData();}/*** 初始化控件*/private void initView() {mTabLayout = findViewById(R.id.tabs);mViewpager = findViewById(R.id.viewpager);}/*** 初始化数据*/private void initData() {fragments = new ArrayList<>(); //实例化fragment集合for (int i = 0; i < tabs.length; i++) {mTabLayout.addTab(mTabLayout.newTab().setText(tabs[i])); //添加Tab，并且设置标题文字//添加三个Fragment实例switch (i) {case 0:fragments.add(ItemFragment.newInstance(0));break;case 1:fragments.add(ItemFragment.newInstance(1));break;case 2:fragments.add(ItemFragment.newInstance(2));break;}}mViewpager.setAdapter(new FragmentAdapter(getSupportFragmentManager(), fragments)); //设置ViewPager设配器mViewpager.setCurrentItem(1);        //设置当前选定页面（这里的值是1，代表初始化是第二个页面）mViewpager.setOffscreenPageLimit(2); //缓存页面个数（这里是缓存了两个页面，）mTabLayout.setupWithViewPager(mViewpager); //建立TabLayout与ViewPager关联，（就是这么牛，一句代码解决关联代码）for (int i = 0; i < tabs.length; i++)mTabLayout.getTabAt(i).setText(tabs[i]);//这个地方主要是解决ViewPager设置设配器的时候，把TabLayout的标题文字给置空问题。}
}