先簡單說一下思路：網路變化時系統會發出廣播。所以我們監聽這個廣播，利用接

口回撥通知activity做相應的操作就好了。

思路

• 判斷網路狀態（寫個工具類NetUtil）

• 寫個類繼承BroadcastReceiver（不要忘記在清單檔案中註冊）

• 需要在清單檔案中新增許可權

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>

• 回撥介面（NetEvevt）

• BaseActivity實現這個介面

直接上程式碼

NetUtil

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;

/**
 * Author: lenovo
 * Date: 2018/2/26
 * email: 
 
[email protected]
 */

public class NetUtil {


    /**
     * 沒有連線網路
     */
    public static final int NETWORK_NONE = -1;
    /**
     * 行動網路
     */
    public static final int NETWORK_MOBILE = 0;
    /**
     * 無線網路
     */
    public static final int NETWORK_WIFI = 1;

    public static int getNetWorkState(Context context) {

        // 得到連線管理器物件
        ConnectivityManager connectivityManager = (ConnectivityManager) context
                .getSystemService(Context.CONNECTIVITY_SERVICE);

        NetworkInfo activeNetworkInfo = connectivityManager
                .getActiveNetworkInfo();
        if (activeNetworkInfo != null && activeNetworkInfo.isConnected()) {
            if (activeNetworkInfo.getType() == (ConnectivityManager.TYPE_WIFI)) {
                return NETWORK_WIFI;
            } else if (activeNetworkInfo.getType() == (ConnectivityManager.TYPE_MOBILE)) {
                return NETWORK_MOBILE;
            }
        } else {
            return NETWORK_NONE;
        }
        return NETWORK_NONE;
    }

}
 

NetBroadReceiver

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;

/**
 * Author: lenovo
 * Date: 2018/2/26
 * email: [email protected]
 */

public class NetBroadcastReceiver extends BroadcastReceiver {
    public NetEvevt evevt = BaseActivity.evevt;

    @Override
    public void onReceive(Context context, Intent intent) {
        // TODO Auto-generated method stub
        // 如果相等的話就說明網路狀態發生了變化
        if (intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION)) {
            int netWorkState = NetUtil.getNetWorkState(context);
            // 介面回撥傳過去狀態的型別
            evevt.onNetChange(netWorkState);
        }
    }

    // 自定義介面
    public interface NetEvevt {
        public void onNetChange(int netMobile);
    }
}
 

BaseActivity

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;

/**
 * Author: lenovo
 * Date: 2018/2/26
 * email: [email protected]
 */

abstract public class BaseActivity extends FragmentActivity implements NetBroadcastReceiver.NetEvevt {

    public static NetBroadcastReceiver.NetEvevt evevt;
    /**
     * 網路型別
     */
    private int netMobile;

    @Override
    protected void onCreate(Bundle arg0) {
        // TODO Auto-generated method stub
        super.onCreate(arg0);
        evevt = this;
        inspectNet();
    }


    /**
     * 初始化時判斷有沒有網路
     */

    public boolean inspectNet() {
        this.netMobile = NetUtil.getNetWorkState(BaseActivity.this);
        return isNetConnect();

        // if (netMobile == 1) {
        // System.out.println("inspectNet：連線wifi");
        // } else if (netMobile == 0) {
        // System.out.println("inspectNet:連線移動資料");
        // } else if (netMobile == -1) {
        // System.out.println("inspectNet:當前沒有網路");
        //
        // }
    }

    /**
     * 網路變化之後的型別
     */
    @Override
    public void onNetChange(int netMobile) {
        // TODO Auto-generated method stub
        this.netMobile = netMobile;
        isNetConnect();

    }

    /**
     * 判斷有無網路 。
     *
     * @return true 有網, false 沒有網路.
     */
    public boolean isNetConnect() {
        if (netMobile == 1) {
            return true;
        } else if (netMobile == 0) {
            return true;
        } else if (netMobile == -1) {
            return false;

        }
        return false;
    }

}

MainActivity

import android.os.Bundle;
import android.view.View;
import android.widget.ListView;
import android.widget.TextView;

public class MainActivity extends BaseActivity {

    private TextView textView,txtView;
    ListView listView;  //宣告一個ListView物件

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        textView= (TextView) findViewById(R.id.textView);
        txtView=(TextView)this.findViewById(R.id.txtView);


        //啟動時判斷網路狀態
        boolean netConnect = this.isNetConnect();
        if (netConnect){
            textView.setVisibility(View.GONE);
            txtView.setText("網路連線正常");
        }else {
            textView.setVisibility(View.VISIBLE);
            txtView.setText("網路連線異常");
        }
    }

    @Override
    public void onNetChange(int netMobile) {
        super.onNetChange(netMobile);
        //網路狀態變化時的操作
        if (netMobile==NetUtil.NETWORK_NONE){
            textView.setVisibility(View.VISIBLE);
            txtView.setText("網路連線異常");
        }else {
            textView.setVisibility(View.GONE);
            txtView.setText("網路連線正常");
        }
    }

}

記得在清單檔案中註冊

<receiver android:name="cn.broadcastreceiver.NetBroadcastReceiver" >  
            <intent-filter>  
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />  
            </intent-filter>  
        </receiver>  

/**
 * Author: lenovo
 * Date: 2018/2/26
 * email: [email protected]
 */