Null Pointer Exception in alert dialog after BOOT_COMPLETED

Question

I want to show an alert dialog when booting of device is completed. There are no problems with the broadcast receiver, it works fine. But when boot is completed, there is no open activity, hence I get NullPointerException here. How can I show a dialog box in this situation? This is the code I use to show the dialog:

public class RestartReceiver extends BroadcastReceiver 
{
    @Override
    public void onReceive(Context context, Intent intent) 
    {

        AlertDialog alertHelp;
        AlertDialog.Builder dialog = new AlertDialog.Builder(context);
        TextView m_timetext = new TextView(context );
        m_timetext.setText("hello");
        //  m_timetext.setTextColor(getResources().getColor(R.color.dark_green));

        LinearLayout linearLayout = new LinearLayout(context );
        linearLayout.setLayoutParams( new  LinearLayout.LayoutParams(LinearLayout.LayoutParams.FILL_PARENT,
                LinearLayout.LayoutParams.FILL_PARENT));
        linearLayout.setOrientation(1); 
        linearLayout.addView(m_timetext);

        dialog.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {

            }});

        dialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {

            }});

        alertHelp = dialog.create();
        alertHelp.setView(linearLayout);
        alertHelp.show();       

        Log.d("In","Switched On");
    }
}

Please help me. Thanks in advance.

Ok, so this is because only Activities can display Dialogs, not BroadCasts. — Carnal, Oct 26 '12 at 07:43
And btw, I don't think it is a good idea of displaying a dialog when the phone starts, it can be annoying for the user using your app. — Carnal, Oct 26 '12 at 07:44
If you still want to achieve the dialog being displayed, you could start a transparent activity, and from that activity display a dialog. — Carnal, Oct 26 '12 at 07:58
You cannot start a Dialog from a broadcastReceiver. What you can do is start an Activity with the dialog Theme. — Benoît Bouré, Oct 26 '12 at 08:03

score 3 · Accepted Answer · edited May 23 '17 at 12:03

Here is a post on how to do it. You can get the source code from here.

Your code doesn't work because you can't show dialog directly from your broadcast receiver. You have to use an Activity. Also, in order to receive ACTION_BOOT_COMPLETED your activity must be first explicitly started by user or by another application (google application stopped state for more information).

Basically, to achieve the required functionality, you need to do:

Create transparent activity that shows dialog.
Create BroadcastReceiver that receives ACTION_BOOT_COMPLETED and starts your activity.
Register your broadcast receiver in the manifest and acquire a proper permission.

Also, this question provides more information on how to create a transparent activity.

Null Pointer Exception in alert dialog after BOOT_COMPLETED

1 Answers1