Android实现ViewPager无限循环效果（一）

本文实例为大家分享了Android实现ViewPager无限循环的具体代码，供大家参考，具体内容如下

方式一：

实现原理：

假设有3张图片，分别是1,2,3，那么就创建5张图片，这5张图片的顺序为：3,1,2,3,1，其中1,2,3为我们要实现滑动的图片，最左面的3和最右面的1是我们另外添加的图片，开始时，显示图片1，当图片向左滑动依次为1,2,3，当从第3张图片继续向左滑动，会出现我们多添加的图片1，这时，将当前的index设置为真正的图片1所在的位置。

package com.xiaomai.myproject.demo;

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

import com.xiaomai.myproject.R;
import com.xiaomai.myproject.adapter.LoopViewPagerAdapter;
import com.xiaomai.myproject.base.BaseActivity;
import com.xiaomai.myproject.utils.Utils;

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

/**
 * Created by XiaoMai on 2016/10/7 17:19.
 *
 */
public class LoopViewPagerDemoActivity extends BaseActivity {

 /**
  * 更新图片的时间
  */
 private static final int UPDATE_TIME = 3 * 1000;

 private ViewPager mViewPager;

 private LoopViewPagerAdapter mLoopViewPager;

 /**
  * 图片资源集合
  */
 private int[] mImageIds;

 /**
  * 图片集合
  */
 private List<ImageView> mImageList;

 /**
  * 当前广告的index
  */
 private int mCurrentPageIndex;

 /**
  * 指示Point
  */
 private LinearLayout mLinearLayoutPoints;

 private Handler mHandler = new Handler();

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
 }

 @Override
 protected void onResume() {
  super.onResume();
  mHandler.postDelayed(myRunnable, UPDATE_TIME);
 }

 @Override
 protected void onPause() {
  super.onPause();
  mHandler.removeCallbacks(myRunnable);
 }

 Runnable myRunnable = new Runnable() {
  @Override
  public void run() {
   mViewPager.setCurrentItem(mCurrentPageIndex + 1);
  }
 };

 @Override
 protected void initVariables() {
  super.initVariables();
 }

 @Override
 protected void initViews() {
  mLinearLayoutPoints = (LinearLayout) findViewById(R.id.activity_ll_container);
  mViewPager = (ViewPager) findViewById(R.id.activity_loop_viewpager);
 }

 @Override
 protected void loadData() {
  super.loadData();
  mHandler.postDelayed(new Runnable() {
   @Override
   public void run() {
    /**
     * 初始化图片的资源id
     */
    mImageIds = new int[]{
      R.mipmap.ic_launcher,
      R.mipmap.ic_launcher,
      R.drawable.my_toast,
      R.drawable.my_toast};
    /**
     * 添加ImageView
     */
    mImageList = new ArrayList<>();
    //额外添加两张图片
    int pagerCount = mImageIds.length + 2;
    ViewGroup.LayoutParams layoutParams =
      new ViewGroup.LayoutParams(
        ViewGroup.LayoutParams.MATCH_PARENT,
        ViewGroup.LayoutParams.WRAP_CONTENT);
    for (int i = 0; i < pagerCount; i++) {
     ImageView imageView = new ImageView(mContext);
     imageView.setLayoutParams(layoutParams);
     mImageList.add(imageView);
    }
    //圆点的直径
    int diameter = Utils.dip2px(mContext,10f);
    LinearLayout.LayoutParams params =
      new LinearLayout.LayoutParams(diameter, diameter);
    int margin = Utils.dip2px(mContext,5f);
    params.setMargins(margin,margin,margin,margin);
    mLinearLayoutPoints.removeAllViews();
    for (int i = 0; i < mImageList.size(); i++) {
     View view = new View(mContext);
     view.setLayoutParams(params);
     if (i != 0 && i != mImageList.size() - 1) {
      view.setBackgroundResource(R.drawable.circle_normal);
     }
     mLinearLayoutPoints.addView(view);
    }
    mLinearLayoutPoints.setVisibility(View.VISIBLE);
    mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
     @Override
     public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

     }

     @Override
     public void onPageSelected(int position) {
      mHandler.removeCallbacks(myRunnable);
      mHandler.postDelayed(myRunnable, UPDATE_TIME);
      mCurrentPageIndex = position;
      if (position == 0) {
       // 当视图在第一个时，将页面号设置为图片的最后一张。
       mCurrentPageIndex = mImageIds.length;
      } else if (position == mImageIds.length + 1) {
       // 当视图在最后一个时,将页面号设置为图片的第一张。
       mCurrentPageIndex = 1;
      } else {
      }
      /**
       * 当视图在第一个或者最后一个时，pageIndex和position的值不相等，
       * 所以要改变viewPager的当前item。
       */
      if (position != mCurrentPageIndex) {
       /**
        * 第二参数必须设置为false，意思是立即过渡，不给用户视觉上的效果。
        */
       mViewPager.setCurrentItem(mCurrentPageIndex, false);
       return;
      }
      for (int i = 1; i < mLinearLayoutPoints.getChildCount() - 1; i++) {
       if (i != mCurrentPageIndex){
        mLinearLayoutPoints.getChildAt(i).setBackgroundResource(R.drawable.circle_normal);
       }else {
        mLinearLayoutPoints.getChildAt(mCurrentPageIndex).setBackgroundResource(
          R.drawable.circle_select);
       }
      }

     }

     @Override
     public void onPageScrollStateChanged(int state) {

     }
    });
    /**
     * 当ViewPager被按下的时候，取消自动滚动
     * 反之开启自动滑动。
     */
    mViewPager.setOnTouchListener(new View.OnTouchListener() {
     @Override
     public boolean onTouch(View v, MotionEvent event) {
      if(event.getAction() == MotionEvent.ACTION_DOWN){
       mHandler.removeCallbacks(myRunnable);
      }else if (event.getAction() == MotionEvent.ACTION_UP){
       mHandler.postDelayed(myRunnable, UPDATE_TIME);
      }
      return false;
     }
    });
    mLoopViewPager = new LoopViewPagerAdapter(mImageList, mImageIds);
    mViewPager.setAdapter(mLoopViewPager);
    /**
     * 因为第0个item是另外添加的那张图片，所以初始化时要把当前item设置为1。
     */
    mViewPager.setCurrentItem(1);
    dissMissProgressDialog();
   }
  }, 3 * 1000);

 }

 @Override
 protected int getContentLayout() {
  return R.layout.act_loopviewpager;
 }
}

package com.xiaomai.myproject.adapter;

import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import java.util.List;

/**
 * Created by XiaoMai on 2016/10/7 17:23.
 */
public class LoopViewPagerAdapter extends PagerAdapter {

 private List<ImageView> mImageList;

 private int[] mImageIds;

 public LoopViewPagerAdapter(List<ImageView> mImageList, int[] mImageIds) {
  this.mImageList = mImageList;
  this.mImageIds = mImageIds;
 }

 @Override
 public int getCount() {
  return mImageList == null ? 0 : mImageList.size();
 }

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

 @Override
 public Object instantiateItem(ViewGroup container, int position) {
  if (position == 0) {
   // 如果是第0个item就设置它的图片内容为最后一个图片的内容
   mImageList.get(position).setImageResource(mImageIds[mImageIds.length-1]);
  } else if (position == (mImageList.size() - 1)) {
   // 如果是最后一个item就设置它的图片内容为第一个图片的内容
   mImageList.get(position).setImageResource(mImageIds[0]);
  } else {
   // 这是正常的图片
   mImageList.get(position).setImageResource(mImageIds[position - 1]);
  }
  container.addView(mImageList.get(position));
  return mImageList.get(position);
 }

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

布局文件

<?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:orientation="vertical">

 <include
  android:id="@+id/titleBar"
  layout="@layout/my_app_bar" />

 <android.support.v4.view.ViewPager
  android:id="@+id/activity_loop_viewpager"
  android:layout_width="match_parent"
  android:layout_height="200dp"
  android:layout_below="@id/titleBar" />

 <LinearLayout
  android:id="@+id/activity_ll_container"
  android:layout_width="match_parent"
  android:orientation="horizontal"
  android:gravity="center"
  android:background="@color/toast"
  android:layout_alignBottom="@id/activity_loop_viewpager"
  android:visibility="gone"
  android:layout_height="40dp"/>
</RelativeLayout>

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。