Android——引导页ViewPager的使用

前言：ViewPager（android.support.v4.view.ViewPager）是android扩展包v4包中的类，这个类可以让用户左右切换当前的view，实现滑动切换的效果。ViewPager最常用于三个场景，分别是应用的新手引导页，广告轮播控件，和Fragment结合做应用内的标签页。

效果图：

1、引导页布局文件activity_guide.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

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

    <LinearLayout
        android:id="@+id/guide_ll_point"
        android:orientation="horizontal"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="40dp"
        android:gravity="center_horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </LinearLayout>

    <ImageButton
        android:id="@+id/guide_ib_start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_above="@+id/guide_ll_point"
        android:src="@mipmap/enter_app"
        android:background="@null"
        android:visibility="gone"/>

</RelativeLayout>
           

2、引导页适配器GuidePageAdapter.java

public class GuidePageAdapter extends PagerAdapter {

    private List<View> viewList;

    public GuidePageAdapter(List<View> viewList) {
        this.viewList = viewList;
    }

    /**
     * 返回页面的个数
     * @return
     */
    @Override
    public int getCount() {
        if (viewList != null) {
            return viewList.size();
        }
        return ;
    }

    /**
     * 判断对象是否生成界面
     * @param view
     * @param object
     * @return
     */
    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == object;
    }

    /**
     * 初始化position位置的页面
     * @param container
     * @param position
     * @return
     */
    @Override
    public Object instantiateItem(ViewGroup container, int position) {
        container.addView(viewList.get(position));
        return viewList.get(position);
    }

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

3、引导页Activity

public class GuideActivity extends AppCompatActivity implements ViewPager.OnPageChangeListener {

    private ViewPager vp;
    private int[] imageIdArray;//图片资源的数组
    private List<View> viewList;//图片资源的集合
    private ViewGroup vg;//放置圆点

    private ImageView iv_point;
    private ImageView[] ivPointArray;

    private ImageButton ib_start;//进入首页的ImageButton

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        supportRequestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.activity_guide);

        ib_start = (ImageButton) findViewById(R.id.guide_ib_start);
        ib_start.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent intent = new Intent(GuideActivity.this,MainActivity.class);
                startActivity(intent);
                finish();
            }
        });

        //加载ViewPager
        initViewPager();

        //加载底部圆点
        initPoint();

        vg.getChildAt().setBackgroundResource(R.mipmap.full_holo);
    }

    /**
     * 加载底部圆点
     */
    private void initPoint() {
        //这里实例化LinearLayout
        vg = (ViewGroup) findViewById(R.id.guide_ll_point);
        //根据viewpager的item数量实例化数组
        ivPointArray = new ImageView[viewList.size()];
        //循环新建底部圆点imageview，将生成的imageview保存到数组中
        int size = viewList.size();
        for (int i = ; i < size; i++) {
            iv_point = new ImageView(this);
            iv_point.setLayoutParams(new ViewGroup.LayoutParams(,));
            iv_point.setPadding(,,,);//left,top,right,bottom
            ivPointArray[i] = iv_point;
            //第一个页面需要设置为选中状态，这里采用两张不同的图片
            if (i == ) {
                iv_point.setImageResource(R.mipmap.full_holo);
            } else {
                iv_point.setImageResource(R.mipmap.empty_holl);
            }
            //将数组中的imageView加到viewGroup
            vg.addView(ivPointArray[i]);
        }
    }

    /**
     * 加载图片ViewPager
     */
    private void initViewPager() {
        vp = (ViewPager) findViewById(R.id.guide_vp);
        //实例化图片资源
        imageIdArray = new int[]{R.mipmap.guide1,R.mipmap.guide2,R.mipmap.guide3};
        viewList = new ArrayList<>();
        //获取一个Layout参数，设置为全屏
        LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
                LinearLayout.LayoutParams.MATCH_PARENT,LinearLayout.LayoutParams.MATCH_PARENT);
        //循环创建View并加入到集合中
        int len = imageIdArray.length;
        for (int i = ; i < len; i++) {
            //new ImageView并设置全屏和图片资源
            ImageView imageView = new ImageView(this);
            imageView.setLayoutParams(params);
            imageView.setBackgroundResource(imageIdArray[i]);

            //将ImageView加入到集合中
            viewList.add(imageView);
        }
        //view集合初始化好后，设置Adapter
        vp.setAdapter(new GuidePageAdapter(viewList));
        //设置滑动监听
        vp.setOnPageChangeListener(this);
    }

    @Override
    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

    }

    /**
     * 滑动后的监听
     * @param position
     */
    @Override
    public void onPageSelected(int position) {
        //循环设置当前页的标记图标
        int length = imageIdArray.length;
        for (int i = ; i < length; i++) {
            if (i == position) {
                vg.getChildAt(position).setBackgroundResource(R.mipmap.full_holo);
            } else {
                vg.getChildAt(i).setBackgroundResource(R.mipmap.empty_holl);
            }
        }

        //判断是否是最后一页
        if (position == imageIdArray.length - ) {
            ib_start.setVisibility(View.VISIBLE);
        } else {
            ib_start.setVisibility(View.GONE);
        }
    }

    @Override
    public void onPageScrollStateChanged(int state) {

    }
}