android编程5.2.1

alltolove

先新建一个项目，修改androidmanifest.xml文件，在manifest标签里添加

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

修改activity_main.xml文件

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.xinwei.broadcasttest.MainActivity">

    <TextView
        android:id="@+id/text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

修改mainactivity.java文件

package com.example.xinwei.broadcasttest;

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.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    private IntentFilter intentFilter;
    NetworkChangeReceiver networkChangeReceiver;
    TextView text;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        intentFilter=new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        networkChangeReceiver=new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver,intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }

    class NetworkChangeReceiver extends BroadcastReceiver{

        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectivityManager=(ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo=connectivityManager.getActiveNetworkInfo();
            if(networkInfo!=null&&networkInfo.isAvailable()){
                text=(TextView)findViewById(R.id.text);
                text.setText("有网");
            }
        }
    }
}

效果图为：