Is there a way to stop USB devices from triggering Android activity's pause/resume cycle?

Question

The following is in AndroidManifest.xml for MainActivity:

   <activity
        android:name=".MainActivity"
        android:configChanges="orientation|keyboardHidden|screenSize"
        android:directBootAware="true"
        android:exported="true"
        android:icon="@mipmap/ic_launcher_round"
        android:launchMode="singleInstance"
        >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
            <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
        </intent-filter>

        <meta-data
            android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
            android:resource="@xml/usb_device_filter" />
    </activity>

If I plug in USB devices A, B, and C for the first time, the OS prompts me to select the app. This is exactly what it should be. After I unplug all of them, then plug them back, MainActivity pauses and resumes three times (i.e., pauses and resumes, and in a fraction of a second, pauses and resumes again, then in a faction of a second, pauses and resumes for the last time). The app is always in the foreground.

This is not a huge problem. It is manageable. I am curious if there is a way to avoid this kind of useless pause/resume cycle when the app is already in the foreground.

Answer 1

Potential Solution:

With no way to test, here is one possible reason this could be happening.

You are running with launchMode as 'singleInstance'. It is possible that the three pause-resume cycles you experience when plugging the three usb devices back are three restart cycles.

Try setting

android:launchMode="singleTop"

Documentation singleTop

If an instance of the activity already exists at the top of the target task, the system routes the intent to that instance through a call to its onNewIntent() method, rather than creating a new instance of the activity.

My reasoning is that singleTop might specifically route the newIntent to the already running instance. It's one possible solution, given the information we have available.

Answer 2

Don't think you can stop it. but you can use a broadcast receiver to detect the attached / detached event and take action from there.

(disclaimer untested)

private final BroadcastReceiver usbReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(action)) {
            // USB device attached, handle it
        } else if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action)) {
            // USB device detached, handle it
        }
    }
};

https://developer.android.com/reference/android/hardware/usb/UsbManager