三无限轮播无原点

最新推荐文章于 2025-06-11 19:13:31 发布

原创最新推荐文章于 2025-06-11 19:13:31 发布 · 289 阅读

CC 4.0 BY-SA版权

本文介绍了一种使用Android实现无限轮播图的方法，通过自定义ViewPager适配器和主线程Handler来达到图片自动轮播的效果，并从服务器获取JSON数据加载图片。

package com.example.wuxianlunbo;

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 com.google.gson.Gson;
import com.nostra13.universalimageloader.core.ImageLoader;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    String path="http://www.meirixue.com/api.php?c=index&a=index";
    private ViewPager vp;
    private List<User.DataBean.AdlistBean> adlist;
    private Madapter madapter;

    //主线程
    Handler handler=new Handler(){
        @Override
        public void handleMessage(Message msg) {
          int what=msg.what;
            switch (what){
                case 0:
                    Object obj = msg.obj;//取出值
                    String s = obj.toString();
                    Gson gson = new Gson();
                    User user = gson.fromJson(s, User.class);
                    adlist = user.getData().getAdlist();
                    //添加适配器
                    madapter = new Madapter();
                    vp.setAdapter(madapter);
                    //设置延时
                    vp.setCurrentItem(1000);
                    handler.sendEmptyMessageDelayed(1,2000);
                    break;
                case 1:
                    int currentItem = vp.getCurrentItem();
                    currentItem++;
                    vp.setCurrentItem(currentItem);
                    handler.sendEmptyMessageDelayed(1,2000);//延时
                    break;
            }
        }
    };



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        vp =(ViewPager)findViewById(R.id.vp);
        init();//添加数据
    }

    private void init() {
        //子线程
        new Thread(){
            @Override
            public void run() {
                try {
                    URL url = new URL(path);
                    HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
                    int responseCode = urlConnection.getResponseCode();
                    if (responseCode==200){
                        InputStream inputStream = urlConnection.getInputStream();
                        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                        StringBuilder builder = new StringBuilder();
                        String string="";
                        while ((string=bufferedReader.readLine())!=null){
                            builder.append(string);
                        }
                        String s = builder.toString();
                        //创建
                        Message me = new Message();
                        me.obj=s;
                        me.what=0;
                        handler.sendMessage(me);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }.start();
    }


    //ViewPager的适配器
    class Madapter extends PagerAdapter{

        @Override
        public int getCount() {
            return Integer.MAX_VALUE;//无限轮播   无限制
        }

        @Override
        public boolean isViewFromObject(View view, Object object) {
            return view==object;
        }


        @Override//创建试图
        public Object instantiateItem(ViewGroup container, int position) {
            ImageView img = new ImageView(MainActivity.this);
            img.setScaleType(ImageView.ScaleType.FIT_XY);//缩放
            ImageLoader.getInstance().displayImage(adlist.get(position%adlist.size()).getImg(),img);
            container.addView(img);
            return img;
        }

        @Override//销毁
        public void destroyItem(ViewGroup container, int position, Object object) {
            container.removeView((View)object);
        }
    }
}

//布局

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