ViewPager +无限轮播+滑动速度修改+指示小点

养成习惯，做过代码记录总结。

ViewPager 使用记录

1. ViewPage 位于V4包。

2.主要用来做banner轮播。

3.原理：适配器重用提高效率，与listview等一个原理。

下面记录实现代码。

一：

在布局里使用ViewPager

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"  
    xmlns:tools="http://schemas.android.com/tools"  
    android:layout_width="fill_parent"  
    android:layout_height="fill_parent"  
    tools:context="com.example.testviewpage_1.MainActivity" >  
  
<android.support.v4.view.ViewPager  
    android:id="@+id/viewpager"  
    android:layout_width="wrap_content"  
    android:layout_height="wrap_content"  
    android:layout_gravity="center" />  
</RelativeLayout> 

二：需要一个适配器 ：PageAdapter ;

 PagerAdapter pagerAdapter = new PagerAdapter() {

        @Override
        public boolean isViewFromObject(View arg0, Object arg1) {
            return arg0 == arg1;
        }

        @Override
        public int getCount() {
            return viewList.size();
        }

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

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            container.addView(viewList.get(position));
            return viewList.get(position);
        }
    };

三：给apapter 加点数据（View）。

private ViewPager viewPager;

private List<View> viewList;

 viewList = new ArrayList<>();
        ImageView iv = new ImageView(getActivity());
        Glide.with(getContext()).load("http://www.shjinheng.com/uploadfile/2016/1130/20161130023058307.jpg").into(iv);
        viewList.add(iv);
        iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[1]).into(iv);
        viewList.add(iv);
        iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[2]).into(iv);
        viewList.add(iv);

关键内容：

对adapter的里解

Base class providing the adapter to populate pages inside of a ViewPager. You will most likely want to use a more specific implementation of this, such as FragmentPagerAdapter orFragmentStatePagerAdapter.

When you implement a PagerAdapter, you must override the following methods at minimum:

instantiateItem(ViewGroup, int)
destroyItem(ViewGroup, int, Object)
getCount()
isViewFromObject(View, Object)
PagerAdapter is more general than the adapters used for AdapterViews. Instead of providing a View recycling mechanism directly ViewPager uses callbacks to indicate the steps taken during an update. A PagerAdapter may implement a form of View recycling if desired or use a more sophisticated method of managing page Views such as Fragment transactions where each page is represented by its own Fragment.

ViewPager associates each page with a key Object instead of working with Views directly. This key is used to track and uniquely identify a given page independent of its position in the adapter. A call to the PagerAdapter method startUpdate(ViewGroup) indicates that the contents of the ViewPager are about to change. One or more calls to instantiateItem(ViewGroup, int) and/ordestroyItem(ViewGroup, int, Object) will follow, and the end of an update will be signaled by a call to finishUpdate(ViewGroup). By the time finishUpdate returns the views associated with the key objects returned by instantiateItem should be added to the parent ViewGroup passed to these methods and the views associated with the keys passed to destroyItem should be removed. The method isViewFromObject(View, Object) identifies whether a page View is associated with a given key object.

A very simple PagerAdapter may choose to use the page Views themselves as key objects, returning them from instantiateItem(ViewGroup, int) after creation and adding them to the parent ViewGroup. A matching destroyItem(ViewGroup, int, Object) implementation would remove the View from the parent ViewGroup and isViewFromObject(View, Object) could be implemented as return view == object;.

PagerAdapter supports data set changes. Data set changes must occur on the main thread and must end with a call to notifyDataSetChanged() similar to AdapterView adapters derived fromBaseAdapter. A data set change may involve pages being added, removed, or changing position. The ViewPager will keep the current page active provided the adapter implements the methodgetItemPosition(Object).

isViewFromObject(View, Object)

功能：该函数用来判断instantiateItem(ViewGroup, int)函数所返回来的Key与一个页面视图是否是代表的同一个视图(即它俩是否是对应的，对应的表示同一个View)

返回值：如果对应的是同一个View，返回True，否则返回False。

instantiateItem (ViewGroup container, int position)

给对应位置一个View

实现循环

有两种办法，一种是把getcount改成

Integer.MAX_VALUE
在dinstantiateItem 方法中 对position取%
然后就是各种坑，这种方法不太好用。
第二种方法是多加两个view 取实际的最后一个放在第一个，实际第一个放在最后一个。
如果是三个数据，那最终viewlist应该是2，0，1，2，0
在onPageSelected方法中当页转到第5页时，调用setCurrentItem方法将当前页设置到1，相反是0的时候设置到2；
看代码

 　　　　 
　　　　　多插入两条内容。
　　　　　viewList = new ArrayList<>();
        ImageView iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[2]).into(iv);
        viewList.add(iv);//多加的

        iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[0]).into(iv);
        viewList.add(iv);

        iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[1]).into(iv);
        viewList.add(iv);

        iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[2]).into(iv);
        viewList.add(iv);

        iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[0]).into(iv);
        viewList.add(iv);//多加的

     viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(final int position) {
                mHandler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        if (position == viewList.size() - 1) {
                            viewPager.setCurrentItem(1, false);//不要动画
                        } else if (position == 0) {
                            viewPager.setCurrentItem(viewList.size() - 2, false);//不要动画
                        }
                    }
                }, 200);//延后执行，改善视觉效果。

            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });

当然要从第二个开始展示

viewPager.setCurrentItem(1);


接下来搞定自动轮播：
handler 来实现。

 Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            viewPager.setCurrentItem((viewPager.getCurrentItem() + 1) % viewList.size());
            mHandler.sendEmptyMessageDelayed(1, 1000);
        }
    };

修改滑动速度.
默认的速度太快,viewpager也没有给出修改办法，还限制了最长不超过600毫秒。
滑动最终还是由scroller完成，我们通过反射来修改viewpager自带scroller ;

package com.lechang.utils;

import android.content.Context;
import android.support.v4.view.ViewPager;
import android.view.animation.Interpolator;
import android.widget.Scroller;

import java.lang.reflect.Field;

/**
 * hongtao 
 */
public class MyScroller extends Scroller {

    private int mDuration = 1500; // default time is 1500ms

    public MyScroller(Context context) {
        super(context);
    }

    public MyScroller(Context context, Interpolator interpolator) {
        super(context, interpolator);
    }

    @Override
    public void startScroll(int startX, int startY, int dx, int dy, int duration) {
        super.startScroll(startX, startY, dx, dy, mDuration);
    }

    @Override
    public void startScroll(int startX, int startY, int dx, int dy) {
        super.startScroll(startX, startY, dx, dy, mDuration);
    }

    /**
     * set animation time
     *
     * @param time
     */
    public void setmDuration(int time) {
        mDuration = time;
    }

    /**
     * get current animation time
     *
     * @return
     */
    public int getmDuration() {
        return mDuration;
    }

    public void acttchToViewPager(ViewPager viewPager) {
        try {
            Field mField = ViewPager.class.getDeclaredField("mScroller");
            mField.setAccessible(true);
            mField.set(viewPager, this);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

//修改滑动速度
MyScroller myScroller = new MyScroller(getContext());
myScroller.setmDuration(2000);
myScroller.attacToViewPager(viewPager);

到此完美实现。

给出完整的类：

package com.lechang.fragment;


import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;

import com.bumptech.glide.Glide;
import com.lechang.R;
import com.lechang.utils.MyScroller;

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

/**
 * @author hongtao
 */
public class QualityFragment extends BaseFragment {


    public QualityFragment() {

    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_quality, container, false);
        init(view);
        return view;
    }

    LinearLayout ll_point;

    String urls[] = {"https://ss0.bdstatic.com/70cFvHSh_Q1YnxGkpoWK1HF6hhy/it/u=150174610,1151432426&fm=27&gp=0.jpg",
            "https://ss0.bdstatic.com/70cFvHSh_Q1YnxGkpoWK1HF6hhy/it/u=1705520648,1030222030&fm=27&gp=0.jpg",
            "https://f10.baidu.com/it/u=2987595138,4271236850&fm=72"};

    public void setPoint(int index) {
        if (index == viewList.size() - 1) {
            index = 1;
        } else if (index == 0) {
            index = viewList.size() - 2;
        }
        for (int i = 0; i < viewList.size() - 1; i++) {
            if (i == (index - 1)) {
                ll_point.getChildAt(i).setBackgroundResource(R.drawable.point_fucsed);
            } else {
                ll_point.getChildAt(i).setBackgroundResource(R.drawable.point_unfucsed);
            }
        }
    }

    public void initPoint() {
        for (int i = viewList.size() - 2; i < ll_point.getChildCount(); i++) {
            ll_point.getChildAt(i).setVisibility(View.GONE);
        }
    }

    public void init(View rootView) {
        ll_point = (LinearLayout) rootView.findViewById(R.id.ll_point);
        viewList = new ArrayList<>();
        ImageView iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[2]).into(iv);
        viewList.add(iv);

        iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[0]).into(iv);
        viewList.add(iv);

        iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[1]).into(iv);
        viewList.add(iv);

        iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[2]).into(iv);
        viewList.add(iv);

        iv = new ImageView(getActivity());
        Glide.with(getContext()).load(urls[0]).into(iv);
        viewList.add(iv);

        viewPager = (ViewPager) rootView.findViewById(R.id.viewpager);
        viewPager.setAdapter(pagerAdapter);
        viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

            }

            @Override
            public void onPageSelected(final int position) {
                mHandler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        if (position == viewList.size() - 1) {
                            viewPager.setCurrentItem(1, false);//不要动画
                        } else if (position == 0) {
                            viewPager.setCurrentItem(viewList.size() - 2, false);//不要动画
                        }
                    }
                }, INTERVAL_TIME);//延后执行，改善视觉效果。
                setPoint(position);
            }

            @Override
            public void onPageScrollStateChanged(int state) {

            }
        });
        viewPager.setCurrentItem(1);
        initPoint();
        //修改滑动速度
        MyScroller myScroller = new MyScroller(getContext());
        myScroller.setmDuration(2000);
        myScroller.attachToViewPager(viewPager);

        mHandler.sendEmptyMessageDelayed(1, INTERVAL_TIME);
    }

    public static final int INTERVAL_TIME = 3000;
    Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            viewPager.setCurrentItem((viewPager.getCurrentItem() + 1) % viewList.size());
            mHandler.sendEmptyMessageDelayed(1, INTERVAL_TIME);
        }
    };


    private ViewPager viewPager;

    private List<View> viewList;


    PagerAdapter pagerAdapter = new PagerAdapter() {

        @Override
        public boolean isViewFromObject(View arg0, Object arg1) {
            return arg0 == arg1;
        }

        @Override
        public int getCount() {
            return viewList.size();
        }

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

        @Override
        public Object instantiateItem(ViewGroup container, int position) {
            container.addView(viewList.get(position));
            return viewList.get(position);
        }
    };


}

配置

<FrameLayout 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"
    tools:context="com.lechang.fragment.QualityFragment">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="150dp">

        <android.support.v4.view.ViewPager
            android:id="@+id/viewpager"
            android:layout_width="match_parent"
            android:layout_height="150dp"
            android:background="#444" />

        <LinearLayout
            android:id="@+id/ll_point"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentBottom="true"
            android:layout_centerHorizontal="true">

            <View
                android:layout_width="5dp"
                android:layout_height="5dp"
                android:layout_margin="5dp"
                android:background="@drawable/point_fucsed" />

            <View
                android:layout_width="5dp"
                android:layout_height="5dp"
                android:layout_margin="5dp"
                android:background="@drawable/point_unfucsed" />

            <View
                android:layout_width="5dp"
                android:layout_height="5dp"
                android:layout_margin="5dp"
                android:background="@drawable/point_unfucsed" />

            <View
                android:layout_width="5dp"
                android:layout_height="5dp"
                android:layout_margin="5dp"
                android:background="@drawable/point_unfucsed" />

            <View
                android:layout_width="5dp"
                android:layout_height="5dp"
                android:layout_margin="5dp"
                android:background="@drawable/point_unfucsed" />
        </LinearLayout>
    </RelativeLayout>


</FrameLayout>

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval"
    android:useLevel="false">

    <solid android:color="#055" />
    <stroke
        android:width="1dp"
        android:color="@color/white" />
    <size
        android:width="5dp"
        android:height="5dp" />
</shape>

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval"
    android:useLevel="false">

    <solid android:color="#f00" />
    <stroke
        android:width="1dp"
        android:color="@color/white" />
    <size
        android:width="5dp"
        android:height="5dp" />
</shape>