android - How to setup Alertbox from BroadcastReceiver

Question

I have implemented alarm in android app. Alarm is working fine. Toast message is visible. Now I want to make Alert Box Notification to user.

Here is code from ReceiverActivity Class. which I tried

public class ReceiverActivity extends BroadcastReceiver{
@Override
public void onReceive(Context context, Intent intent) {
    // TODO Auto-generated method stub

// Code....


    new AlertDialog.Builder(context)
    .setTitle("Alert Box")
    .setMessage("Msg for User")
    .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface arg0, int arg1) {
        // TODO Auto-generated method stub
            // some coding...
        }
    })
    .setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface arg0, int arg1) {
            arg0.dismiss();
    }
}).create().show();
}

}

Answer 1

---

Although you can not show AlertDialog from Receivers because it needs ActivityContext.

You have an alternate solution to show an Activity like AlertDialog from Receiver. This is possible.

To start Activity as dialog you should set theme of activity in manifest as <activity android:theme="@android:style/Theme.Dialog" />

Style Any Activity as an Alert Dialog in Android

---

To start Activity from Receiver use code like

    //Intent mIntent = new Intent();
    //mIntent.setClassName("com.test", "com.test.YourActivity"); 
    Intent mIntent = new Intent(context,YourActivity.class) //Same as above two lines
    mIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    context.startActivity(mIntent);

---

And one more reason behind not using AlertDialog from receiver (Even if you managed to show AlertDialog) is

A BroadcastReceiver object is only valid for the duration of the call to onReceive(Context, Intent). Once your code returns from this function, the system considers the object to be finished and no longer active.

This has important repercussions to what you can do in an onReceive(Context, Intent) implementation: anything that requires asynchronous operation is not available, because you will need to return from the function to handle the asynchronous operation, but at that point the BroadcastReceiver is no longer active and thus the system is free to kill its process before the asynchronous operation completes.

In particular, you may not show a dialog or bind to a service from within a BroadcastReceiver. For the former, you should instead use the NotificationManager API. For the latter, you can use Context.startService() to send a command to the service. More...

So the better way is 'show notification' and alternate way is 'to use Activity as an Alert..'

Happy coding :)