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{ 
   
  private ViewPager viewPager; 
   
  private ImageView[] tips; 
   
  private ImageView[] mImageViews; 
   
  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); 
  } 
   
  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]); 
    } 
     
    @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); 
  } 
   
  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]; 
  } 

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