I am trying to make an app that shows a toast when the device's Bluetooth turned on. I wanna do that even when my app is not running. So I should use a broadcast receiver, add some permissions, an intent-filter to android manifest and make a java class but I don't know the details.
What should I do? Which permissions should I use?
AS far as permissions go, to detect the state change of bluetooth you need to add this to your AndroidManifest.xml.
<uses-permission android:name="android.permission.BLUETOOTH" />
An example receiver would look like this, you add this code to where you want to handle the broadcast, for example an activity:
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
public void onReceive (Context context, Intent intent) {
String action = intent.getAction();
if (BluetoothAdapter.ACTION_STATE_CHANGED.equals(action)) {
if(intent.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1)
== BluetoothAdapter.STATE_OFF)
// Bluetooth is disconnected, do handling here
}
}
};
To use the receiver, you need to register it. Which you can do as follows. I register the receiver in my main activity.
registerReceiver(this, new IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED));
You could also decide to add all of it to your AndroidManifest.xml. This way you can make a special class for the receiver and handle it there. No need to register the receiver, just make the class and add the below code to the AndroidManifest
<receiver
android:name=".packagename.NameOfBroadcastReceiverClass"
android:enabled="true">
<intent-filter>
<action android:name="android.bluetooth.adapter.action.STATE_CHANGED"/>
</intent-filter>
</receiver>
You have to take following permission.
<uses-permission android:name="android.permission.BLUETOOTH" />
and you have to write this as your intent filter in receiver tag.
<action android:name="android.bluetooth.adapter.action.STATE_CHANGED" />
Unfortunately, for apps targeting api 26 or higher, manifest declared broadcast receivers don't work anymore (reference here: https://developer.android.com/guide/components/broadcast-exceptions), with some exceptions.
android.bluetooth.adapter.action.STATE_CHANGED is not in that list.
For bluetooth, you can only listen for changes on:
ACTION_CONNECTION_STATE_CHANGED, ACTION_ACL_CONNECTED, ACTION_ACL_DISCONNECTED
