网络工具,通过该类可以直接监听网络状态改变

package com.bearbaby.erp.staff.util;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.widget.Toast;

import com.bearbaby.erp.staff.MyApplication;

import java.util.ArrayList;
import java.util.List;
/**
 * Created by Administrator on 2017/4/19.
 */

public class NetUtils {
    private static boolean netStateLink = true;
    private static boolean registered = false;//防止重复注册
    private static boolean showToasted = false;  //防止application和启动页面重复初始化后,没网络提示语的重复
    private static Context context;
    private static NetUtils instance;
    private static ConnectionChangeReceiver myNetReceiver;
    private static final String TAG = "NetUtils";
    private NetUtils() {
    }
    public static synchronized NetUtils getInstance() {    //对获取实例的方法进行同步
        if (instance == null)
            instance = new NetUtils();
        return instance;
    }
    //获得是否有网络连接
    public static boolean isnetStateLink() {
        LogUtil.i(TAG, "isnetStateLink:是否有网络?"+netStateLink);
        return netStateLink;
    }
    /**
     * 这个一定要调用一次
     * 否则应用无法联网一定要在网络请求之前调用
     *启动页面初始化就好 为了安全起见,application一定要调用,startup也要调用,
     * 因为用户返回键退出后,不会再走application的创建,(应用退出,但是不杀死进程不会走application的)
     * @param contexts 一定要是Context,不能是Activity的this
     */
    public static void init(Context contexts) {
        if (contexts != null) {
            context = contexts;
            ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo mobNetInfo = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
            NetworkInfo wifiNetInfo = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
            if (!mobNetInfo.isConnected() && !wifiNetInfo.isConnected()) {
                netStateLink = false;
                if (!showToasted){
                    Toast.makeText(context,"联网失败,请检查网络设置",Toast.LENGTH_SHORT) .show();
                    showToasted=true;
                }
                LogUtil.i(TAG, "isnetStateLink:  初始化网络状态没有网络连接.........");
            } else {
                LogUtil.i(TAG, "isnetStateLink:  初始化网络状态有网络连接.........");
                netStateLink = true;
            }
            if (!registered){
                registerReceiver();//注册.......
            }
        }
    }
    /**
     * 注册网络监听
     */
    private static void registerReceiver() {
        LogUtil.i(TAG, " 注册网络监听registerReceiver.........");
        IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
        myNetReceiver = new ConnectionChangeReceiver();
        context.registerReceiver(myNetReceiver, filter);
        registered=true;
    }
    /**
     * 取消网络注册监听
     * 需要在应用最后一个页面销毁后注销(MainActivity退出后一定要调用),
     * 不然提示第一次进入后的联网失败,请检查网络设置,会重复
     */
    public static void unregisterReceiver() {
        LogUtil.i(TAG, " 反注册网络监听unregisterReceiver.........");
        if (registered){
            try {
                if (context!=null){
                    context.unregisterReceiver(myNetReceiver);
                    LogUtil.i(TAG, " 成功反注册网络监听.........");
                    registered=false;
                }
            } catch (Exception e) {
                e.printStackTrace();
                LogUtil.e(TAG, "异常反注册网络监听........."+e.getMessage());
                registered=false;
            }
            registered=false;
        }
        showToasted=false;
    }
    static List<NetworkState> ln = new ArrayList();
    //网络状态监听
    static class ConnectionChangeReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo mobNetInfo = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
            NetworkInfo wifiNetInfo = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
            if (!mobNetInfo.isConnected() && !wifiNetInfo.isConnected()) {
                    if (netStateLink) {
                        if ( MyApplication.getContext().isAppVisible()) {
                            ToastUtil.show("网络已断开!");
                            for (NetworkState ns : ln) {
                                if (ns != null) {
                                    ns.disconnectNetwork();
                                }
                            }
                        }
                    }
                netStateLink = false;
            } else {
                    if (!netStateLink){
                        if ( MyApplication.getContext().isAppVisible()) {
                            ToastUtil.show("网络已恢复!");
                            //通知监听,如果不在前台不通知,防止有网络后,做其他网络操作退出回到登录页面
                            netStateLink = true;//这个必须要在回调前修改为true 因为接口后面可能会有网络操作,到时候任然无法请求
                            for (NetworkState ns : ln) {
                                if (ns != null) {
                                    ns.connectedNetwork();
                                }
                            }
                        }
                    }
                netStateLink = true;
            }
        }
    }
    //添加网络监听和removeNetworkListen搭配
    public void addNetworkListen(NetworkState ns) {
        if (ns != null) {
            ln.add(ns);
        }
    }
    //网络状态监听回调接口
    public interface NetworkState {
        //连接上网络
        void connectedNetwork();
        //断开网络
        void disconnectNetwork();
    }
    //移除网络监听,和addNetworkListen搭配使用
    public synchronized void　　en(NetworkState ns) {
        if (ns != null) {
            for (int i = 0; i < ln.size(); i++) {
                if (ln.get(i) == ns) {
                    ln.remove(i);
                }
            }
        }
    }
}