Android巧用ViewPager实现左右循环滑动图片

ViewPager这个小demo实现的是可以左右循环滑动图片，下面带索引，滑到最后一页在往右滑动就要第一页，第一页往左滑动就到最后一页，先上效果图：

1、首先看一些layout下的xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="fill_parent"
 android:layout_height="fill_parent"
 android:orientation="vertical" >

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

<RelativeLayout  
   android:layout_width="fill_parent"  
   android:layout_height="wrap_content"  
   android:orientation="vertical" >  

<LinearLayout  
     android:id="@+id/viewGroup"  
     android:layout_width="fill_parent"  
     android:layout_height="wrap_content"  
     android:layout_alignParentBottom="true"  
     android:layout_marginBottom="30dp"  
     android:gravity="center_horizontal"  
     android:orientation="horizontal" >  
   </LinearLayout>  
 </RelativeLayout>  

</FrameLayout>

 使用ViewPager首先需要引入Android-support-v4.jar这个jar包，自己不要忘记加

package com.example.viewpagerdemo;

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.view.ViewGroup.LayoutParams;
import android.widget.ImageView;
import android.widget.LinearLayout;

public class TwoActivity extends Activity implements OnPageChangeListener{
 /**
  * ViewPager
  */
 private ViewPager viewPager;

/**
  * 装点点的ImageView数组
  */
 private ImageView[] tips;

/**
  * 装ImageView数组
  */
 private ImageView[] mImageViews;

/**
  * 图片资源id
  */
 private int[] imgIdArray ;

@Override
 protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_main);
   ViewGroup group = (ViewGroup)findViewById(R.id.viewGroup);
   viewPager = (ViewPager) findViewById(R.id.viewPager);

//载入图片资源ID
   imgIdArray = new int[]{R.drawable.item01, R.drawable.item02, R.drawable.item03, R.drawable.item04,
       R.drawable.item05,R.drawable.item06, R.drawable.item07, R.drawable.item08};

//将点点加入到ViewGroup中
   tips = new ImageView[imgIdArray.length];
   for(int i=0; i<tips.length; i++){
     ImageView imageView = new ImageView(this);
     imageView.setLayoutParams(new LayoutParams(10,10));
     tips[i] = imageView;
     if(i == 0){
       tips[i].setBackgroundResource(R.drawable.page_indicator_focused);
     }else{
       tips[i].setBackgroundResource(R.drawable.page_indicator_unfocused);
     }

LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(new ViewGroup.LayoutParams(LayoutParams.WRAP_CONTENT,  
         LayoutParams.WRAP_CONTENT));
     layoutParams.leftMargin = 5;
     layoutParams.rightMargin = 5;
     group.addView(imageView, layoutParams);
   }

//将图片装载到数组中
   mImageViews = new ImageView[imgIdArray.length];
   for(int i=0; i<mImageViews.length; i++){
     ImageView imageView = new ImageView(this);
     mImageViews[i] = imageView;
     imageView.setBackgroundResource(imgIdArray[i]);
   }

//设置Adapter
   viewPager.setAdapter(new MyAdapter());
   //设置监听，主要是设置点点的背景
   viewPager.setOnPageChangeListener(this);
   //设置ViewPager的默认项, 设置为长度的100倍，这样子开始就能往左滑动
   viewPager.setCurrentItem((mImageViews.length) * 100);

}

/**
  *
  * @author xiaanming
  *
  */
 public class MyAdapter extends PagerAdapter{

@Override
   public int getCount() {
     return Integer.MAX_VALUE;
   }

@Override
   public boolean isViewFromObject(View arg0, Object arg1) {
     return arg0 == arg1;
   }

@Override
   public void destroyItem(View container, int position, Object object) {
     ((ViewPager)container).removeView(mImageViews[position ％ mImageViews.length]);

}

/**
    * 载入图片进去，用当前的position 除以 图片数组长度取余数是关键
    */
   @Override
   public Object instantiateItem(View container, int position) {
     ((ViewPager)container).addView(mImageViews[position ％ mImageViews.length], 0);
     return mImageViews[position ％ mImageViews.length];
   }

}

@Override
 public void onPageScrollStateChanged(int arg0) {

}

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

}

@Override
 public void onPageSelected(int arg0) {
   setImageBackground(arg0 ％ mImageViews.length);
 }

/**
  * 设置选中的tip的背景
  * @param selectItems
  */
 private void setImageBackground(int selectItems){
   for(int i=0; i<tips.length; i++){
     if(i == selectItems){
       tips[i].setBackgroundResource(R.drawable.page_indicator_focused);
     }else{
       tips[i].setBackgroundResource(R.drawable.page_indicator_unfocused);
     }
   }
 }

}

源码下载：左右滑动ViewPager 

2、上面的代码中，当只有3张图片或者2张图片的时候，滑动存在BUG问题的修改如下
destroyItem(View container, int position, Object object)方法中不removeView

@Override
   public void destroyItem(View container, int position, Object object) {
//     ((ViewPager)container).removeView(mImageViews[position ％ mImageViews.length]);
   }
instantiateItem(View container, int position)增加异常扑捉

@Override
 public Object instantiateItem(View container, int position) {
   try {  
     ((ViewPager)container).addView(mImageViews[position ％ mImageViews.length], 0);
   }catch(Exception e){
     //handler something
   }
   return mImageViews[position ％ mImageViews.length];
 }