Question

How do I display dialog from a service?

Answer 1

android-smspopup does exactly that.

A service receives a sms and it starts an Activity with:

android:theme="@android:style/Theme.Dialog"

EDIT: The dialog activity is started here with this code

private void notifyMessageReceived(SmsMmsMessage message) {
    (...)
    context.startActivity(message.getPopupIntent());
    (...)
}

With getPopupIntent() declared as followed (code here):

public Intent getPopupIntent() {
    Intent popup = new Intent(context, SmsPopupActivity.class);
    popup.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);
    popup.putExtras(toBundle());
    return popup;
    }

SmsPopupActivity class obviously defines the dialog activity. Its declared as followed in AndroidManifest.xml:

    <activity
        android:name=".ui.SmsPopupActivity"
        android:configChanges="keyboardHidden|orientation|screenSize"
        android:launchMode="singleTask"
        android:screenOrientation="user"
        android:taskAffinity="net.everythingandroid.smspopup.popup"
        android:theme="@style/DialogTheme" >
    </activity>