Goals
- If a bluetooth device connects, and no Activity is running, start Activity
- If a bluetooth device connects, and an Activity is already running, connect to the already running Activity
Problem
- As soon as a device connects, a new Activity starts. I have not been able to make the app reuse the same Activity.
What I have managed to solve
- If a bluetooth device connects, and no Activity is running, start Activity
The problem manifests itself in the use of BroadCastReceivers which in turn starts the Activity using intents. For some reason the Activity keep running through its lifecycle, spawning up new windows, when a new device connects.
I've tested this solely on a Nexus 6P with Android N. I have no idea yet what kind of implications this implementation means for any other devices yet. But I at least need to get this working on one device.
Manifest
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.VIBRATE" />
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".BtActivity" />
<receiver android:name=".BtConnectionBroadcastReceiver" android:priority="100000">
<intent-filter>
<action android:name="android.bluetooth.device.action.ACL_CONNECTED" />
<action android:name="android.bluetooth.device.action.ACL_DISCONNECTED" />
<action android:name="android.bluetooth.device.action.ACL_DISCONNECT_REQUESTED" />
<action android:name="android.intent.action.MEDIA_BUTTON" />
<action android:name="android.media.VOLUME_CHANGED_ACTION" />
</intent-filter>
</receiver>
</application>
BtConnectionBroadcastReceiver
public class BtConnectionBroadcastReceiver extends BroadcastReceiver {
private static final String TAG = "BT";
public static final String BROADCAST_ACTION_CONNECTED = "CONNECTED";
public static final String BROADCAST_ACTION_DISCONNECTED = "DISCONNECTED";
SharedPreferences mSharedPreferences;
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// When discovery finds a device
if (BluetoothDevice.ACTION_ACL_CONNECTED.equals(action)) {
// Get the BluetoothDevice object from the Intent
Log.d(TAG, "DEVICE CONNECTED");
BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
Log.d("DEVICE NAME", device.getName());
Log.d("DEVICE ADDRESS", device.getAddress());
Intent i = new Intent(context, BtActivity.class);
context.startActivity(i);
} else if (BluetoothDevice.ACTION_ACL_DISCONNECTED.equals(action)) {
Log.d(TAG, "DEVICE DISCONNECTED");
intent = new Intent();
intent.setAction(BtConnectionBroadcastReceiver.BROADCAST_ACTION_DISCONNECTED);
context.sendBroadcast(intent);
}
}
BtActivity
public class BtActivity extends AppCompatActivity {
private static final String TAG = "BT";
Window mWindow;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_bt);
Log.d(TAG, "onCreate");
IntentFilter filter = new IntentFilter(BtConnectionBroadcastReceiver.INTENT_FILTER);
filter.addAction(BtConnectionBroadcastReceiver.BROADCAST_ACTION_CONNECTED);
filter.addAction(BtConnectionBroadcastReceiver.BROADCAST_ACTION_DISCONNECTED);
//registerReceiver(mReceiver, filter);
mWindow = getWindow();
WindowManager.LayoutParams params = new WindowManager.LayoutParams();
//params.screenBrightness = WindowManager.LayoutParams.BRIGHTNESS_OVERRIDE_OFF;
params.screenBrightness = 0.2f;
mWindow.setAttributes(params);
mWindow.addFlags(WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);
mWindow.addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED);
mWindow.addFlags(WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON);
mWindow.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
mWindow.addFlags(WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE);
mWindow.getDecorView().setSystemUiVisibility(
View.SYSTEM_UI_FLAG_LAYOUT_STABLE |
View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION |
View.SYSTEM_UI_FLAG_HIDE_NAVIGATION |
View.SYSTEM_UI_FLAG_FULLSCREEN |
View.SYSTEM_UI_FLAG_IMMERSIVE);
}
@Override
protected void onResume() {
super.onResume();
Log.d(TAG, "onResume");
}
@Override
protected void onDestroy() {
super.onDestroy();
Log.d(TAG, "onDestroy");
}
}
When I run this code, I get the following chain:
- Start MainActivity (not included, it only contains an activity with the default main layout, so that the applications receiver is registered)
- Switch on a bluetooth device (This has been paired earlier, so android knows about it)
- Wait until it connects and get this:
- DEVICE CONNECTED
- onCreate
- onResume
I can't grasp why the activity is restarting at this point. The activity is already running, the BroadcastReceiver only sends a broadcast to an already running activity. I can't figure out why there's a reason for the Activity to kill itself and then restart again.
