Android实现轮播图片展示效果

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package com.example.a2_;

import android.os.Handler;
import android.os.Message;
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 {
private static final int UPDATE_ITEM = 1;
private ArrayList imageViews = new ArrayList<>();
private int[] imageResIds = {R.mipmap.icon_1, R.mipmap.icon_2, R.mipmap.icon_3,
  R.mipmap.icon_4, R.mipmap.icon_5};

private String[] descs = {"为梦想坚持", "我相信我是黑马", "黑马公开课", "Google/IO", "轻松1w+"};
private ViewPager viewPager;
private TextView tv_desc;
private LinearLayout layout_dot;
private int count = 10000000;
private Handler handler = new Handler() {
 @Override
 public void handleMessage(Message msg) {
  switch (msg.what) {
   case UPDATE_ITEM:
    upDataItem();
    break;
  }
  super.handleMessage(msg);
 }
};

@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);

 //初始化控件
 viewPager = (ViewPager) findViewById(R.id.vp);
 tv_desc = (TextView) findViewById(R.id.desc);
 layout_dot = (LinearLayout) findViewById(R.id.layout_dot);
 //给viewPager设置适配器
 viewPager.setAdapter(new MyPagerAdapter());
 //对viewPager设置监听器
 viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {

  //当页面滚动时触发的时间
  @Override
  public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

  }

  //当页面被选中时触发的方法
  @Override
  public void onPageSelected(int position) {
   //对position进行处理
   position = position % imageViews.size();
   //当页面被选中的时候,改变描述文本
   tv_desc.setText(descs[position]);
   changeDots(position);
  }

  //当页面状态滚动状态发生改变时触发的事件
  @Override
  public void onPageScrollStateChanged(int state) {
   //当页面空闲状态被改变的时候
   if (state == viewPager.SCROLL_STATE_IDLE) {
    handler.sendEmptyMessageDelayed(UPDATE_ITEM, 3000);
   } else {
    handler.removeMessages(UPDATE_ITEM);
   }
  }
 });


 //初始化图片
 initImage();
 //初始化文字下方的点
 initDot();
 //当加载页面的时候,默认让第一个文本加载出来
//  initDescFirst();

 //使两边都可以无限轮播
 viewPager.setCurrentItem(count / 2);
//页面加载时更新
 upDataItem();
}

private void upDataItem() {
 int index = viewPager.getCurrentItem();
 viewPager.setCurrentItem(++index);
 handler.sendEmptyMessageDelayed(UPDATE_ITEM, 3000);
}

//选中对应的原点
private void changeDots(int position) {
 //先把所有的点恢复为白色
 for (int i = 0; i