经过ViewPager 实现图片轮播

经过ViewPager 实现图片轮播

首先来个效果图

布局文件：

LinearLayout 用来存放下方的几个小白点。

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                xmlns:tools="http://schemas.android.com/tools"
                android:id="@+id/activity_view_pager"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                tools:context="com.example.it.controlstudy.ViewPagerActivity">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:layout_centerHorizontal="true">

        <android.support.v4.view.ViewPager
            android:id="@+id/viewPager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"/>

        <LinearLayout
            android:id="@+id/whitePoins_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom"
            android:gravity="center_horizontal"
            android:orientation="horizontal"
            android:padding="5dp">
        </LinearLayout>
    </FrameLayout>

</RelativeLayout>

咱们要经过shape自定义一个图片来实现小白点显示。

这个图片是当作ImageView的背景色来用的。

1. 建立文件

1. 自定义shape

shape:形状 size:大小 solid：填充色

蓝色的：

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="oval">  
    <size       
        android:width="10dp"
        android:height="10dp"/>
    <solid android:color="#22aadc"/>
</shape>

白色的：

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="oval">
    <size
        android:width="10dp"
        android:height="10dp"/>
    <solid android:color="#ffffff"/>
</shape>

代码部分

• 定义控件 集合

private List<ImageView> imageViewsList; //存放全部轮播图片的集合
      private int images[];  //存放全部图片Id
      private List<ImageView> imagePointsList; //存放小白点的ImageView集合 实现小白点功能
      private int pageIndex = 0;  //当前Viewpager页码

      private LinearLayout whitePointsLayout;  //全部小白点将会加到这个布局当中
      private ViewPager viewPager;

• 初始化控件 集合

viewPager = (ViewPager) findViewById(R.id.viewPager);
      whitePointsLayout = (LinearLayout) findViewById(R.id.whitePoins_layout);
      imagePointsList = new ArrayList<>();
      imageViewsList = new ArrayList<>();
    //将图片加载到数组当中
      images = new int[]{R.drawable.shanghai1, R.drawable.shanghai2, R.drawable.shanghai3};

for (int i = 0; i < images.length; i++) {
            //加载轮播图片ImageView集合
            ImageView iv = new ImageView(ViewPagerActivity.this);
            //  经过Glide 加载图片
            Glide.with(ViewPagerActivity.this).load(images[i]).into(iv);
            imageViewsList.add(iv);

            // 加载小白点ImageView集合
            ImageView ivPoint = new ImageView(ViewPagerActivity.this);
            ivPoint.setImageResource(R.drawable.bg_white);
            //动态设置 Margins 属性 ，就是给每一个小白点之间设置间距
            LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
                 LinearLayout.LayoutParams.WRAP_CONTENT,LinearLayout.LayoutParams.WRAP_CONTENT);
            lp.setMargins(10, 10, 10, 10);
            ivPoint.setLayoutParams(lp);

            whitePointsLayout.addView(ivPoint); //将小白点图片添加到LinearLayout布局界面当中
            imagePointsList.add(ivPoint); 
        }
        imagePointsList.get(0).setImageResource(R.drawable.bg_blue); //默认选中第一个小白点为蓝色

• 设置ViewPager 的 PagerAdapter

PagerAdapter adapter = new PagerAdapter() {
            @Override
            public int getCount() {
                return imageViewsList.size();
            }

            @Override
            public boolean isViewFromObject(View view, Object object) {
                return view == object;
            }

            @Override  //设置当前显示View
            public void setPrimaryItem(ViewGroup container, int position, Object object) {
                //首先将全部点设置为白色
                for (int i = imagePointsList.size() - 1; i >= 0; i--) {
                    imagePointsList.get(i).setImageResource(R.drawable.bg_white);
                }
                //再将选中的点设置为蓝色
                imagePointsList.get(position).setImageResource(R.drawable.bg_blue); 
                pageIndex = position; //获取当前Pager的Index

                super.setPrimaryItem(container, position, object);
            }

            @Override   //添加View 
            public Object instantiateItem(ViewGroup container, int position) {
                container.addView(imageViewsList.get(position));
                return imageViewsList.get(position);
            }

            @Override   //销毁不用的View
            public void destroyItem(ViewGroup container, int position, Object object) {
                container.removeView(imageViewsList.get(position));
            }

        };

        //设置适配器
        viewPager.setAdapter(adapter);

---

最后经过Timer实现图片自动切换

//自动切换
 Timer timer = new Timer();
 TimerTask task = new TimerTask() {
     @Override
     public void run() {
         if (pageIndex < (imageViewsList.size() - 1)) {
             pageIndex++;
         } else { //最后一张后切换为第一页
             pageIndex = 0;
         }
         runOnUiThread(new Runnable() {
             @Override
             public void run() {
                 //设置选中的白点
                 imagePointsList.get(pageIndex).setImageResource(R.drawable.bg_blue); 
                 //设置viewPager现实的页面            false 表示不显示动画效果
                 viewPager.setCurrentItem(pageIndex, false);
             }
         });
     }
 };    //表示一开始暂停5秒，而后每3秒执行一次run方法
 timer.schedule(task, 5000, 3000);