[android实现轮播图无限循环]Android实现轮播图无限循环效果

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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

packagecom.tsh.myviewpager;

importjava.util.ArrayList;

importjava.util.List;

importandroid.app.Activity;

importandroid.os.Bundle;

importandroid.support.v4.view.PagerAdapter;

importandroid.support.v4.view.ViewPager;

importandroid.support.v4.view.ViewPager.OnPageChangeListener;

importandroid.view.View;

importandroid.view.ViewGroup;

importandroid.widget.ImageView;

importandroid.widget.LinearLayout;

importandroid.widget.TextView;

publicclassMainActivityextendsActivity {

  privateViewPager vp_banner;

  privateLinearLayout ll_points;

  privateTextView tv_title;

  privateListbanners;

  privateString[] titles=newString[]{

      "新闻标题1",

      "新闻标题2",

      "新闻标题3"

  };

  privateListpoints=newArrayList();

  @Override

  protectedvoidonCreate(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 =newArrayList<>();

    ImageView img1 =newImageView(this);

    img1.setImageResource(R.drawable.a);

    banners.add(img1);

    ImageView img2 =newImageView(this);

    img2.setImageResource(R.drawable.b);

    banners.add(img2);

    ImageView img3 =newImageView(this);

    img3.setImageResource(R.drawable.c);

    banners.add(img3);

    //小图标

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

    for(inti=0;i

      ImageView image=newImageView(this);

      image.setImageResource(R.drawable.point_selector);

      LinearLayout.LayoutParams params=newLinearLayout.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(newMyPagerAdapter());

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

    vp_banner.setOnPageChangeListener(newOnPageChangeListener() {

      @Override

      publicvoidonPageSelected(intarg0) {

        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

      publicvoidonPageScrolled(intarg0,floatarg1,intarg2) {

        // TODO Auto-generated method stub

      }

      @Override

      publicvoidonPageScrollStateChanged(intarg0) {

        // TODO Auto-generated method stub

      }

    });

  }

  privateclassMyPagerAdapterextendsPagerAdapter {

    @Override

    publicvoiddestroyItem(ViewGroup container,intposition, Object object) {

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

      container.removeView((View)object);

      object=null;

    }

    @Override

    publicObject instantiateItem(ViewGroup container,intposition) {

      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));

      }

      returnbanners.get(position);

    }

    @Override

    publicintgetCount() {

      returnInteger.MAX_VALUE;

    }

    @Override

    publicbooleanisViewFromObject(View arg0, Object arg1) {

      returnarg0 == arg1;

    }

  }

}

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