Android 广播

Posted 2020-06-08

广播:

• 有序广播

  • 发出广播之后同一时刻只有一个广播接收器能够接收到广播,优先级高的先接受,可以截断正在传递的广播,后面的就无法收到广播消息了.

• 动态创建广播:

  • 创建一个类继承BroadcastReceiver,重写onReceive,有广播来到就会执行onReceive方法,动态注册的一定要取消注册.

    public class MainActivity extends Activity {
    private IntentFilter intentFilter;
    private NetworkChangeReceiver networkChangeReceiver;
    
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        intentFilter = new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");// 当系统发生变化时发出的是值为括号内的广播,想要监听什么广播就添加相应的action
        networkChangeReceiver = new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver, intentFilter);// 注册广播
    }
    
    protected void onDestroy() {
        super.onDestroy();
        // 动态注册的一定要取消注册
        unregisterReceiver(networkChangeReceiver);
    }
    
    class NetworkChangeReceiver extends BroadcastReceiver {
        // 每当网络发生变化就会执行此方法
        public void onReceive(Context arg0, Intent arg1) {
            //系统服务类,用来管理网络连接
            ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connectivityManager
                    .getActiveNetworkInfo();
    
            if (networkInfo != null && networkInfo.isAvailable()) {
                Toast.makeText(MainActivity.this, "网络可用", 0).show();
            }else{
                Toast.makeText(MainActivity.this, "网络不可用", 0).show();
            }
    
        }
    
    }
    

    }

• 静态注册实现开机自启

  • 创建一个类,继承自BroadcastReceiver,收到广播就会执行onReceive方法

        public class BootCompleteReceiver extends BroadcastReceiver {
    
    public void onReceive(Context arg0, Intent arg1) {
        Toast.makeText(arg0, "开机",0).show();
    
    }}
    

  • 清单文件注册:

    <receiver android:name=".BootCompleteReceiver" >
    <intent-filter>
        <action android:name="android.intent.action.BOOT_COMPLETED" />
    </intent-filter>
    

     

• 发送自定义广播:

  • 首先构建一个intent对象,然后调用Context的sendBroadcast()方法把广播发送出去,这样所有监听这条广播的都会接受到消息

    Intent intent = new Intent("com.example.broadcasttest.MY_BROADCAST");
    sendBroadcast(intent);
    

• 发送有序广播

  Intent intent = new Intent("com.example.broadcasttest.MY_BROADCAST");
  sendOrderedBroadcast(intent, null);
  

  • 在注册清单的intent-filter中添加android:priority="100"属性来设置优先级,优先级越高越先收到.可以使用abortBroadcast();将广播截断.

• 本地广播

  • 在应用程序的内部进行传递,并且广播接收器只能接受来自本应用的广播

    public class MainActivity extends Activity {
        private LocalReceiver localReceiver;
        private IntentFilter intentFilter;
        private LocalBroadcastManager localBroadcastManager;
    
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            localBroadcastManager = LocalBroadcastManager.getInstance(this);
    
            intentFilter = new IntentFilter();
            intentFilter.addAction("com.example.broadcasttest.LOCAL_BROADCAST");
            localReceiver = new LocalReceiver();
            localBroadcastManager.registerReceiver(localReceiver, intentFilter);
            //注册本地广播监听器
        }
    
    
        public void click(View v){
            Intent intent = new Intent("com.example.broadcasttest.LOCAL_BROADCAST");
            localBroadcastManager.sendBroadcast(intent);//发送本地广播
    
        }
        class LocalReceiver extends BroadcastReceiver {
    
            public void onReceive(Context context, Intent arg1) {
                Toast.makeText(context, "received local broadcast",
                        Toast.LENGTH_SHORT).show();
            }
    
        }
        protected void onDestroy() {
            super.onDestroy();
            localBroadcastManager.unregisterReceiver(localReceiver);
        }
    
    }
    

- 系统级别的弹窗

    AlertDialog.Builder builder = new AlertDialog.Builder(context);
    builder.setTitle("强制下线");
    builder.setMessage("在他处登录,你被强制下线");
    builder.setCancelable(false);//设置不可取消
    builder.setPositiveButton("OK",new OnClickListener() {

        public void onClick(DialogInterface arg0, int arg1) {
            //TODO
        }
    });
    AlertDialog dialog = builder.create();
    dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);
    dialog.show();