利用viewPager制作轮播图

利用ViewPager这个demo实现的是可以左右循环滑动图片，类似于web焦点图的效果，简单大方，效果使用。

Layout布局

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="160dp" >

        <android.support.v4.view.ViewPager
            android:id="@+id/viewpager"
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="40dp"
            android:padding="5dp"
            android:orientation="vertical"
            android:layout_alignParentBottom="true"
            android:gravity="center_horizontal"
            android:background="#66000000" >

            <TextView
                android:id="@+id/tv_desc"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textColor="@android:color/white"
                android:singleLine="true" />
            
            <LinearLayout 
                android:id="@+id/ll_point_container"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginTop="5dp"
                android:orientation="horizontal"
                ></LinearLayout>
        </LinearLayout>
    </RelativeLayout>

</RelativeLayout>

MainActivity

• ViewPager在Android-support-v4.jar这个jar包下，所以不要导错jar包
• 自定义MyAdapter继承自PagerAdapter
• 监听ViewPager的图片改变OnPageChangeListener

• 通过记录上一次的图片的位置lastPosition来修改焦点原点的显示状态

  package com.declan.viewpager;
  
  import android.support.v4.view.PagerAdapter;
  import android.support.v4.view.ViewPager;
  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.view.View;
  import android.view.ViewGroup;
  import android.widget.ImageView;
  import android.widget.LinearLayout;
  import android.widget.TextView;
  
  import java.util.ArrayList;
  
  public class MainActivity extends AppCompatActivity implements ViewPager.OnPageChangeListener {
  
      private ViewPager viewPager;
      private TextView tv_desc;
      private LinearLayout ll_point_container;
      private int[] resourceId;  //图片资源集合
      private ArrayList<ImageView> list;  //imageview资源集合
      private LinearLayout.LayoutParams layoutParams;
      private String[] contentDesc;  //文字描述资源集合
      private int lastPosition = 0;
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
  
          initUI();
          initData();
          initAdapter();
  
      }
      private void initUI() {
          viewPager = (ViewPager) findViewById(R.id.viewPager);
          viewPager.addOnPageChangeListener(this);
          tv_desc = (TextView) findViewById(R.id.tv_desc);
          ll_point_container = (LinearLayout) findViewById(R.id.ll_point_container);
      }
  
      /**
       * 初始化数据，包括图片资源、文字资源
       */
      private void initData() {
          //图片资源集合
          resourceId = new int[]{
                  R.drawable.a,R.drawable.b, R.drawable.c, R.drawable.d, R.drawable.e
          };
          //文字集合
          contentDesc = new String[]{
                  "1111",
                  "2222",
                  "3333",
                  "4444",
                  "5555"
          };
          ImageView imageView;
          View pointView;
          list = new ArrayList<ImageView>();
          for(int i = 0;i < resourceId.length;i ++){
              imageView = new ImageView(this);
              imageView.setImageResource(resourceId[i]);
              list.add(imageView);
  
              //给视图添加小白点
              pointView = new View(this);
              pointView.setBackgroundResource(R.drawable.selector_bg);
              layoutParams = new LinearLayout.LayoutParams(10, 10);
              if(i != 0){
                  layoutParams.leftMargin = 15;
              }
              pointView.setEnabled(false);
              ll_point_container.addView(pointView,layoutParams);
          }
      }
  
      /**
       * 初始化适配器
       * 可以将viewPager近似看成横向的listView
       */
      private void initAdapter() {
          //第一次进入初始化数据
          ll_point_container.getChildAt(0).setEnabled(true);
          tv_desc.setText(contentDesc[0]);
          viewPager.setAdapter(new MyAdapter());
      }
  
      /**
       * 自定义适配器,继承自PagerAdapter
       */
       class MyAdapter extends PagerAdapter{
  
           @Override
           public int getCount() {
               return list.size();
           }
  
           @Override
           public boolean isViewFromObject(View view, Object object) {
               return view == object;
           }
  
           @Override
           public Object instantiateItem(ViewGroup container, int position) {
               ImageView imageView = list.get(position);
               container.addView(imageView);
               return imageView;
           }
  
           @Override
           public void destroyItem(ViewGroup container, int position, Object object) {
               container.removeView((View)object);
           }
       }
  
      @Override
      public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
  
      }
  
      @Override
      public void onPageSelected(int position) {
          //新的条目被选中时调用
          tv_desc.setText(contentDesc[position]);
          ll_point_container.getChildAt(position).setEnabled(true);
          ll_point_container.getChildAt(lastPosition).setEnabled(false);
          lastPosition = position;
      }
  
      @Override
      public void onPageScrollStateChanged(int state) {
  
      }
  }