Android实现轮播图片展示效果

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:tools="http://schemas.android.com/tools"android:id="@+id/activity_main"android:layout_width="match_parent"android:layout_height="match_parent"tools:context="com.example.a2_.MainActivity"><android.support.v4.view.ViewPager  android:id="@+id/vp"  android:layout_width="match_parent"  android:layout_height="250dp"></android.support.v4.view.ViewPager><LinearLayout  android:orientation="vertical"  android:gravity="center"  android:background="#66000000"  android:layout_alignBottom="@id/vp"  android:layout_width="match_parent"  android:layout_height="50dp">  <TextView    android:id="@+id/desc"    android:text="描述文本"    android:textColor="#ffffff"    android:layout_width="wrap_content"    android:layout_height="wrap_content" />  <LinearLayout    android:id="@+id/layout_dot"    android:orientation="horizontal"    android:layout_width="wrap_content"    android:layout_height="wrap_content">  </LinearLayout></LinearLayout></RelativeLayout>

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<ImageView> 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);  }};@Overrideprotected 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 < layout_dot.getChildCount(); i++) {    View view = layout_dot.getChildAt(i);    view.setSelected(false);  }  //获取当前被选中的条目 设置为选中状态  layout_dot.getChildAt(position).setSelected(true);}//初始化文字下方的点private void initDot() {  LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(10, 10);  layoutParams.setMargins(4, 4, 4, 4);  for (int i = 0; i < imageViews.size(); i++) {    View view = new View(this);    view.setBackgroundResource(R.drawable.seletor_dot);    view.setLayoutParams(layoutParams);    layout_dot.addView(view);  }}//当加载页面的时候,默认让第一个文本加载出来private void initDescFirst() {  tv_desc.setText(descs[0]);  changeDots(0);}//添加图片,准备一个ImageView集合,用来交给instantiateItem添加到页面private void initImage() {  for (int i = 0; i < imageResIds.length; i++) {    //创建出ImageView对象    ImageView imageView = new ImageView(getApplicationContext());    imageView.setImageResource(imageResIds[i]);    imageViews.add(imageView);  }}private class MyPagerAdapter extends PagerAdapter {  @Override  public int getCount() {    return count;  }  @Override  public boolean isViewFromObject(View view, Object object) {    //判断这个view是不是通过instantiateItem创建出来的    return view == object;  }  //用来创建条目  @Override  public Object instantiateItem(ViewGroup container, int position) {    position = position % imageResIds.length;    //获取条目    ImageView imageView = imageViews.get(position);    container.addView(imageView);    return imageView;  }  //用来销毁条目,,且最多会创建出三个条目,多出来的条目将会被销毁  @Override  public void destroyItem(ViewGroup container, int position, Object object) {    //销毁创建的条目    container.removeView((View) object);  }}@Overrideprotected void onStart() {  super.onStart();  //当页面显示的时候,更新轮播图  handler.sendEmptyMessageDelayed(UPDATE_ITEM, 3000);}@Overrideprotected void onStop() {  super.onStop();  //当页面不可见时,停止更新  handler.removeCallbacksAndMessages(null);}}