如何使用广播接收器向布局中的对象发送命令？

Question

I am using a service and a broadcast receiver. When the service is started it will put a notification in the user's notification center that returns a START_STICKY. I added an action button to that notification that will stop the service. That part works fine, but I also have a switch object on my activity_main.xml layout that I want it to uncheck when the user taps on that action button to stop the service if the user still has that layout opened, and in focus on their screen at the time they tapped on that action button.

I thought the solution was as easy as using a LayoutInflater, but it's not working for me.

Here is what I tried... I put the following code in the onReceive method in my Broadcast Receiver class. All the other stuff that I have in that method is working fine except for this part in question.

LayoutInflater inflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE);
View v = inflater.inflate(R.layout.activity_main, null);
Switch sw = (Switch) v.findViewById(R.id.mySwitch);
sw.setChecked(false);

You would think that would work. I'm telling it to look at a specific layout, and then I told it to execute a uncheck command to the switch object that exists on that layout from the action button in the notification. It's not receiving the command.

Any ideas? I appreciate the help!!

[enter image description here] ( https://i.stack.imgur.com/8UKu6.jpg )

If it helps my project can be downloaded here... enter link description here

Here are my new changes...

Broadcast Receiver Class

public static String ACTION_TURN_OFF_THE_LIGHTS = "com.mathiasapps.lightsonexample.action.TURN_OFF_THE_LIGHTS";


Intent actionStopIntent = new Intent(this, actionTurnOffReceiver.class);
        actionStopIntent.setAction(ACTION_TURN_OFF_THE_LIGHTS);
        PendingIntent actionStopPI = PendingIntent.getBroadcast(this, 0, actionStopIntent, PendingIntent.FLAG_UPDATE_CURRENT);

MainActivity Class

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

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

        IntentFilter filter = new IntentFilter(ACTION_TURN_OFF_THE_LIGHTS);
        registerReceiver(receiver, filter);

    private final MyActivityReceiver receiver = new MyActivityReceiver();

    @SuppressLint("UseSwitchCompatOrMaterialCode")
    public Switch sw;


    class MyActivityReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {
            @SuppressLint("UseSwitchCompatOrMaterialCode")
            Switch sw = findViewById(R.id.lights_on_switch);
            sw.setChecked(false);
        }
    }

Answer 1

Here is what I tried... I put the following code in the onReceive method in my Broadcast Receiver class. All the other stuff that I have in that method is working fine except for this part in question.

LayoutInflater inflater = (LayoutInflater) context.getSystemService(context.LAYOUT_INFLATER_SERVICE); View v = inflater.inflate(R.layout.activity_main, null); Switch sw = (Switch) v.findViewById(R.id.mySwitch); sw.setChecked(false);

You would think that would work.

No, you would not.

I'm telling it to look at a specific layout, and then I told it to execute a uncheck command to the switch object that exists on that layout from the action button in the notification.

No, you're not.

Your Problem

You are inflating a brand new instance of your main activity layout, finding the switch within that layout, and setting that switch - which is NOT the switch in your activity - to unchecked. You are not touching your actual Activity layout by doing this.

A Solution

You need to register a broadcast receiver with the Activity so the actual running instance of the Activity can receive the broadcast and toggle the switch that it contains. See the documentation for an example.

Pseudocode (should go without saying, this is not tested and is meant to guide you towards the solution):

class MyActivity {
    // The receiver that will listen for the "off" broadcast
    class MyActivityReceiver : BroadcastReceiver {
        // When this receiver gets notified, call the owning activity's method
        void onReceive(Intent intent) {
            turnOffToggle();
        }
    }

    private final MyActivityReceiver receiver = new MyActivityReceiver();

    protected void onCreate(...) {
        super.onCreate(...)

        // Register the receiver so we get notified while this activity is active
        IntentFilter filter = // create filter for your broadcast intent
        registerReceiver(receiver, filter);
    }

    proteced void onDestroy() {
        // Stop listening once we're killed
        unregisterReceiver(receiver);
    }

    private void turnOffToggle() {
        // Find the switch in THIS active Activity's layout
        Switch sw = (Switch) findViewById(R.id.mySwitch);
        sw.setChecked(false);
    }
}

---

Edit after questions:

1 - when you set up the action you're targeting the service's local receiver with your intent:

// Will only invoke `actionTurnOffReceiver` declared in the service.
Intent actionStopIntent = new Intent(this, actionTurnOffReceiver.class);

You need a more generic intent any receiver (ie, the one in the activity) can listen for.

// ACTION_TURN_OFF_THE_LIGHTS is some string like "com.my.package.action.TURN_OFF_THE_LIGHTS"
Intent actionStopIntent = new Intent(this, ACTION_TURN_OFF_THE_LIGHTS)

2 - Your activity registration is too generic:

// This is blindly registering for all broadcasts - or Android will just ignore it
IntentFilter filter = new IntentFilter();
registerReceiver(receiver, filter);

As is shown in the example in the documentation I linked to, you have to set up your filter to match the intent you care about. In this case, it's for the "turn off" action:

IntentFilter filter = new IntentFilter(ACTION_TURN_OFF_THE_LIGHTS);
registerReceiver(receiver, filter);

Please review the entire section on Broadcasts so you have a better understanding of how they work. And here's a Medium article that goes into Broadcast Receivers.