Question

15.1. 动态注册

		
package cn.netkiller.broadcast;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private IntentFilter intentFilter;
    private MyBroadcastReceiver myBroadcastReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        intentFilter = new IntentFilter();
        //为过滤器添加处理规则
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        myBroadcastReceiver = new MyBroadcastReceiver();
        //注册广播接收器
        registerReceiver(myBroadcastReceiver, intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        //注销动态的广播接收器
        unregisterReceiver(myBroadcastReceiver);
    }

    //自定义内部类，继承 BroadcastReceiver
    public class MyBroadcastReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {
            Toast.makeText(context, "网络状态已改变", Toast.LENGTH_SHORT).show();
        }
    }
}
		
		
		

现在尝试改变网络状态，例如开启或关闭飞行模式，程序会弹出 "网络状态已改变"。

我的测试环境是 Android 9 Pie 没有加入下面的权限仍然能工作

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

优化程序

		
package cn.netkiller.broadcast;

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

public class MainActivity extends AppCompatActivity {

    private IntentFilter intentFilter;
    private MyBroadcastReceiver myBroadcastReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        intentFilter = new IntentFilter();
        //为过滤器添加处理规则
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        intentFilter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
        intentFilter.addAction(Intent.ACTION_BATTERY_CHANGED);
        intentFilter.addAction(Intent.ACTION_BATTERY_LOW);

        myBroadcastReceiver = new MyBroadcastReceiver();
        //注册广播接收器
        registerReceiver(myBroadcastReceiver, intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        //注销动态的广播接收器
        unregisterReceiver(myBroadcastReceiver);
    }

    //自定义内部类，继承 BroadcastReceiver
    public class MyBroadcastReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
            //判断是否联网
            if (networkInfo != null && networkInfo.isConnected()) {
                Toast.makeText(context, "网络已连接", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(context, "网络不可用", Toast.LENGTH_SHORT).show();
            }

            int status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, -1);
            boolean isCharging = status == BatteryManager.BATTERY_STATUS_CHARGING ||
                    status == BatteryManager.BATTERY_STATUS_FULL;

            if (isCharging) {
                Toast.makeText(context, "正在充电", Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(context, "电池已经充满", Toast.LENGTH_SHORT).show();
            }

            int chargePlug = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
            boolean usbCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_USB;
            boolean acCharge = chargePlug == BatteryManager.BATTERY_PLUGGED_AC;
            if (usbCharge) {
                Toast.makeText(context, "USB 充电", Toast.LENGTH_SHORT).show();
            }

        }
    }
}