[android] 轮播图-无限循环

实现无限循环

在getCount()方法中，返回一个很大的值，Integer.MAX_VALUE

在instantiateItem()方法中，获取当前View的索引时，进行取于操作，传递进来的int position是个非常大的数，对他进行求余数

在destroyItem()方法中，同样

在onPageSelected()监听方法中，对传递进来的索引进行取于

反向的无限循环

调用ViewPager对象的setCurrentItem()方法，设置第一次进来时候的当前页，参数：int数字，我们把它定位到Integer.MAX_VALUE的中间，并且保证第一条是当前位置，Integer.MAX_VALUE/2-((Integer.MAX_VALUE/2)%banners.size())

目前有个左划空白页的问题没解决

package com.tsh.myviewpager;

import java.util.ArrayList;

import java.util.List;

import android.app.Activity;

import android.os.Bundle;

import android.support.v4.view.PagerAdapter;

import android.support.v4.view.ViewPager;

import android.support.v4.view.ViewPager.OnPageChangeListener;

import android.view.View;

import android.view.ViewGroup;

import android.widget.ImageView;

import android.widget.LinearLayout;

import android.widget.TextView;

public class MainActivity extends Activity {

    private ViewPager vp_banner;

    private LinearLayout ll_points;

    private TextView tv_title;

    private List<View> banners;

    private String[] titles=new String[]{

            "新闻标题1",

            "新闻标题2",

            "新闻标题3"

    };

    private List<ImageView> points=new ArrayList<ImageView>();

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        // 初始化

        vp_banner = (ViewPager) findViewById(R.id.vp_banner);

        ll_points = (LinearLayout) findViewById(R.id.ll_points);

        tv_title = (TextView) findViewById(R.id.tv_title);

        // banner部分

        banners = new ArrayList<>();

        ImageView img1 = new ImageView(this);

        img1.setImageResource(R.drawable.a);

        banners.add(img1);

        ImageView img2 = new ImageView(this);

        img2.setImageResource(R.drawable.b);

        banners.add(img2);

        ImageView img3 = new ImageView(this);

        img3.setImageResource(R.drawable.c);

        banners.add(img3);

        //小图标

        ll_points=(LinearLayout) findViewById(R.id.ll_points);

        for(int i=0;i<banners.size();i++){

            ImageView image=new ImageView(this);

            image.setImageResource(R.drawable.point_selector);

            LinearLayout.LayoutParams params=new LinearLayout.LayoutParams(5, 5);

            params.rightMargin=4;

            image.setLayoutParams(params);

            if(i==0){

                image.setEnabled(true);

            }else{

                image.setEnabled(false);

            }

            points.add(image);

            ll_points.addView(image);

        }

        // 设置适配器

        vp_banner.setAdapter(new MyPagerAdapter());

        vp_banner.setCurrentItem(Integer.MAX_VALUE/2-((Integer.MAX_VALUE/2)%banners.size()));

        vp_banner.setOnPageChangeListener(new OnPageChangeListener() {

            @Override

            public void onPageSelected(int arg0) {

                tv_title.setText(titles[arg0%banners.size()]);

                //小图标处理

                for(ImageView point:points){

                    point.setEnabled(false);

                }

                points.get(arg0%banners.size()).setEnabled(true);

            }

            @Override

            public void onPageScrolled(int arg0, float arg1, int arg2) {

                // TODO Auto-generated method stub

            }

            @Override

            public void onPageScrollStateChanged(int arg0) {

                // TODO Auto-generated method stub

            }

        });

    }

    private class MyPagerAdapter extends PagerAdapter {

        @Override

        public void destroyItem(ViewGroup container, int position, Object object) {

            System.out.println("销毁："+position);

            container.removeView((View)object);

            object=null;

        }

        @Override

        public Object instantiateItem(ViewGroup container, int position) {

            System.out.println("初始化："+position);

            position=position%banners.size();

            //解决右划出错

            if(banners.get(position).getParent()!=null){

                //container.removeView(banners.get(position));

            }else{

                container.addView(banners.get(position));

            }

            return banners.get(position);

        }

        @Override

        public int getCount() {

            return Integer.MAX_VALUE;

        }

        @Override

        public boolean isViewFromObject(View arg0, Object arg1) {

            return arg0 == arg1;

        }

    }

}