USB Permissions without prompt

问题:

I have 2 activities within my app. Say FirstActivity and SecondActivity. FirstActivity is the MAIN and LAUNCHER activity. SecondActivity uses usb devices. I want the prompt for USB permission to appear only once within lifetime of the app.

If there was only one Activity, the following lines in manifest solved my purpose:

<activity android:name=".FirstActivity">
    <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>

This was doing the following:

1. Launching FirstActivity whenever usb device (mentioned in xml) is connected is app is not already open.
2. Prompt for usb device permission appears only once.

How do I modify this to achieve the following:

3. If SecondActivity is already running and a new usb device is attached, I must be able to use the device without relaunching the app. So I have written a broadcast receiver for the same as follows:

   public class TriggerReceiver extends BroadcastReceiver {
   
       @Override
       public void onReceive(Context context, Intent intent) {
           if (intent.getAction().equals(UsbManager.ACTION_USB_DEVICE_ATTACHED)) { 
           read connected usb devices and register serial port call listener back.
       }
   }    
   

But the problem is FirstActivity gets relaunched again when usb device is attached while SecondActivity is running. How do I avoid this ?

Will add more information if needed. Would be thankful for any help.

回答1:

Try "remove" intent filter <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" /> from FirstActivity like in this question

Update

FirstActivity triggers on every USB_DEVICE_ATTACHED (even SecondActivity is running) because You set <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" /> filter for it in AndroidManifest.xml file. So You should disable this filter when SecondActivity running. You can do this by that way:

1) add (e.g. AliasFirstActivity) in AndroidManifest.xml to your FirstActivity and move <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" /> filter to alias description (You should remove <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />from FirstActivity description) like that:

        <activity-alias
            android:targetActivity=".FirstActivity"
            android:name=".AliasFirstActivity"
            android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>

            <intent-filter>
                <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/device_filter" />
        </activity-alias>

2) add this code to onCreate() (or to onResume()) of SecondActivity

PackageManager pm = getApplicationContext().getPackageManager();
        ComponentName compName =
                new ComponentName(getPackageName(), getPackageName() + ".AliasFirstActivity");
        pm.setComponentEnabledSetting(
                compName,
                PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
                PackageManager.DONT_KILL_APP);

to suppress intent filter USB_DEVICE_ATTACHED for FirstActivity. You should have in SecondActivity something like that:

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

        triggerReceiver = new TriggerReceiver();

        IntentFilter filter = new IntentFilter();
        filter.addAction(UsbManager.ACTION_USB_DEVICE_ATTACHED);
        registerReceiver(triggerReceiver, filter);

        PackageManager pm = getApplicationContext().getPackageManager();
        ComponentName compName =
                new ComponentName(getPackageName(), getPackageName() + ".AliasFirstActivity");
        pm.setComponentEnabledSetting(
                compName,
                PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
                PackageManager.DONT_KILL_APP);
    }

That should solve Your issue. 3) if it is needed, You can restore <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" /> filter for FirstActivity in onDestroy() (or in onPause()) of SecondActivity by using this code:

    PackageManager pm = getApplicationContext().getPackageManager();
    ComponentName compName =
            new ComponentName(getPackageName(), getPackageName() + ".AliasFirstActivity");
    pm.setComponentEnabledSetting(
            compName,
            PackageManager.COMPONENT_ENABLED_STATE_ENABLED,
            PackageManager.DONT_KILL_APP);

回答2:

But the problem is FirstActivity gets relaunched again when usb device is attached while SecondActivity is running. How do I avoid this?

This is not hard to answer. In your AndroidManifest.xml you literally declare that your FirstActivity should be launched when the event android.hardware.usb.action.USB_DEVICE_ATTACHED occurs.

If you want to handle this event in SecondActivity only, then you have to declare it in the manifest accordingly, for example:

    <activity android:name=".FirstActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <activity android:name=".SecondActivity" android:launchMode="singleTask">
        <intent-filter>
            <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/device_filter" />
    </activity>

Now, whenever your USB device is plugged in, SecondActivity will be launched only. If SecondActivity is already running, then it won't be launched again (or multiple times) because of the attribute android:launchMode="singleTask" specified for SecondActivity. You can read more about the different launch modes here if you're interested.

Since you declared in your manifest that SecondActivity should be launched when a USB device is plugged in, the Android system will ask you the following question:

After ticking the checkbox "Use by default for this USB device", it won't ask you again. Now, everytime you plug in the USB device, your SecondActivity will be launched and it will automatically receive the required USB permissions too.

Let me know if that answers your question.

回答3:

May be this answer help you: USB device access pop-up supression?

From this answer for your activity:

public class UsbEventReceiverActivity extends Activity
 {   
    public static final String ACTION_USB_DEVICE_ATTACHED = "com.example.ACTION_USB_DEVICE_ATTACHED";
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
    }

@Override
protected void onResume()
{
    super.onResume();

    Intent intent = getIntent();
    if (intent != null)
    {
        if (intent.getAction().equals(UsbManager.ACTION_USB_DEVICE_ATTACHED))
        {
            Parcelable usbDevice = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);

            // Create a new intent and put the usb device in as an extra
            Intent broadcastIntent = new Intent(ACTION_USB_DEVICE_ATTACHED);
            broadcastIntent.putExtra(UsbManager.EXTRA_DEVICE, usbDevice);

            // Broadcast this event so we can receive it
            sendBroadcast(broadcastIntent);
        }
    }

    // Close the activity
    finish();
}

}