android - 检查所有 Activity 的互联网并在网络断开时显示消息

Question

目标

这是我想做的:

1. 在我的应用程序的所有 Activity 中始终检查互联网连接(到目前为止我有大约 13 个 Activity )。
2. 如果网络正常，则一切正常。
3. 如果网络不工作，显示一条消息(使用 RelativeLayout)，该消息将在用户离线时显示，即直到网络再次工作，该消息将在那里(无论用户进行什么 Activity )

以前的尝试

这是我尝试过的:

1. 我试图创建一个扩展 Broadcast Receiver 的类。我在所有 Activity 上创建了该类的一个对象并注册了接收器。
2. 在我的类中，每当网络状态发生变化时，主类通过Intent向activity发送消息，然后activity接收并检查消息(代码如下)。

这里是问题:

1. 我从来没有取消注册接收器，这当然会给我一个错误。

   Are you missing a call to unregisterReceiver()?
   

2. 如果我取消注册接收器，它会给我以下错误:

   java.lang.IllegalArgumentException: Receiver not registered
   

Activity 中的代码

// The onCreate function (Just a sample)

onCreate(){
            registerReceiver(broadcastReceiver, new IntentFilter("broadCastName"));
}

// Outside OnCreate
NetworkStatus broadcastReceiver =  new NetworkStatus() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String message;
        Bundle b = intent.getExtras();
        message = b.getString(KEY_NET_MESSAGE);

        if (message.equals(KEY_NET_DISCONNECTED)){
            Toast.makeText(SignupActivity.this, MESSAGE_NET_DISCONNECTED, Toast.LENGTH_SHORT).show();
            btnSignup.setEnabled(false);
            Network_disconnection.setVisibility(View.VISIBLE);
        }
        if (message.equals(KEY_NET_CONNECTED)){
            btnSignup.setEnabled(true);
            Network_disconnection.setVisibility(View.INVISIBLE);
        }

    }
};

//onStop, just a sample
@Override
protected void onStop() {
    unregisterReceiver(broadcastReceiver);
    super.onStop();
}

AndroidManifest.xml

<receiver android:name=".Common.NetworkStatus">
        -
        <intent-filter>
            <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
        </intent-filter>
    </receiver>

网络状态.java

public class NetworkStatus extends BroadcastReceiver implements Keys.UniversalKeys{

@Override
public void onReceive(Context context, Intent arg1) {

    boolean isConnected = arg1.getBooleanExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY, false);
    if(isConnected){
        Intent i = new Intent("broadCastName");
        // Data you need to pass to activity
        i.putExtra(KEY_NET_MESSAGE, KEY_NET_DISCONNECTED);

        context.sendBroadcast(i);
    }
    else{

        Intent i = new Intent("broadCastName");
        // Data you need to pass to activity
        i.putExtra(KEY_NET_MESSAGE, KEY_NET_CONNECTED);

        context.sendBroadcast(i);
        Toast.makeText(context, KEY_NET_CONNECTED, Toast.LENGTH_LONG).show();
    }
}
}

问题

我做错了什么？我很清楚一件事，也许我不应该为每个 Activity 创建新的接收器!另外，为什么我需要制作一个额外的java文件？我的意思是为什么我不能在每个 Activity 上创建一个 BroadcastReceiver 对象并继续它？

Answer 1

了解 XML 与 JAVA

当您在 AndroidMainfest.XML 中注册接收器时，它是静态的。即使应用程序关闭，它也会运行。

当您在 JAVA(Activity)中注册接收器时，它是动态的，可以通过动态编码注册和取消注册。

解决方案

1. 使用以下代码创建一个类 SampleActivity.java:

   public class SampleActivity extends AppCompatActivity {
       // Declare BroadcastReceiver and RelativeLayout
       BroadcastReceiver breceiver;
       RelativeLayout NoNetBar;
   
   
       @Override
           protected void onResume() {
               Toast.makeText(SampleActivity.this, "App has Resumed", Toast.LENGTH_SHORT).show();
   
               // Register your receiver upon resume.
               registerReceiver(breceiver, new IntentFilter("broadCastName"));
               Toast.makeText(SampleActivity.this, "Broadcast Registered", Toast.LENGTH_SHORT).show();
               super.onResume();
           }
   
           public void setRelative(RelativeLayout param_bar) {
               Toast.makeText(SampleActivity.this, "NoNetBar has been setup", Toast.LENGTH_SHORT).show();
               // This will set RelativeLayout to your desired RelativeLayout from your main activity
               NoNetBar = param_bar;
           }
   
           @Override
           protected void onCreate(@Nullable Bundle savedInstanceState) {
               // Call super oncreate and then set RelativeLayout to invisible initially
               super.onCreate(savedInstanceState);
   
               NoNetBar.setVisibility(View.INVISIBLE);
   
               // Initialize broadcast receiver
               breceiver = new BroadcastReceiver() {
                   @Override
                   public void onReceive(Context context, Intent intent) {
           boolean isConnected = intent.getBooleanExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY, false);
                       if (isConnected){
                           NoNetBar.setVisibility(View.VISIBLE);
                       } else if (!isConnected){
                           NoNetBar.setVisibility(View.INVISIBLE);
                       }
   
                   }
               };
               Toast.makeText(SampleActivity.this, "Broadcast Initialized", Toast.LENGTH_SHORT).show();
   
   
               Toast.makeText(SampleActivity.this, "App is Created", Toast.LENGTH_SHORT).show();
           }
   
           @Override
           protected void onPause() {
               super.onPause();
               Toast.makeText(SampleActivity.this, "App has Paused", Toast.LENGTH_SHORT).show();
   
               // Unregister your receiver
               unregisterReceiver(breceiver);
               Toast.makeText(SampleActivity.this, "Broadcast UnRegistered", Toast.LENGTH_SHORT).show();
           }
   }
   

这个类扩展了 AppCompatActivity(像往常一样)。除了少数异常(exception)，您可以使用此类在您希望接收器工作的任何地方创建 Activity 。

1. 在其他 Activity 中使用这个类如下:

   public class MainActivity extends SampleActivity {
   
       Button btnNext;
       RelativeLayout Network_disconnection;
   
       @Override
       protected void onCreate(Bundle savedInstanceState) {
           // Make sure that you can setRelative before calling super.onCreate or you will get a NULL POINTER EXCEPTION
           setRelative(Network_disconnection);
   
           Toast.makeText(MainActivity.this, "Now Calling Supper", Toast.LENGTH_SHORT).show();
           super.onCreate(savedInstanceState);
   
       }
   }
   

2. 您可以查看此链接以了解 Activity 生命周期:
   https://developer.android.com/training/basics/activity-lifecycle/starting.html或者如果赶时间，请查看此图片: