Java Question Problem with Java Code / Library

FabioG · Dec 24, 2013

I would like to create a library in order to flash the LED notification so colorful

I wrote this code in Eclips

B4X:

package net.snclab.lednotificationcontrol;

import android.app.Notification;
import android.app.NotificationManager;
import android.content.Context;
import android.graphics.Color;
import anywheresoftware.b4a.BA.Author;
import anywheresoftware.b4a.BA.ShortName;
import anywheresoftware.b4a.BA.Version;

@ShortName("LedNotificationControl")
@Author("FabioG")
@Version(1.0f)


public class LedNotificationControl {

    private Context mContext;
 
    public void LedFlashColor(int A, int R, int G, int B) 
    {
    NotificationManager nm = ( NotificationManager ) mContext.getSystemService(Context.NOTIFICATION_SERVICE);
    Notification notif = new Notification();
    notif.ledARGB = Color.argb(A, R, G, B);
    notif.flags = Notification.FLAG_SHOW_LIGHTS; //Notification.DEFAULT_LIGHTS;
    notif.ledOnMS = 100;
    notif.ledOffMS = 100;
    nm.notify(0, notif);
    }
 
 
    public void ClearLED()
    {
    NotificationManager nm = ( NotificationManager ) mContext.getSystemService( Context.NOTIFICATION_SERVICE );
    nm.cancel(0);
    }
 
}

but when I use it in B4A I get this error

B4X:

java.lang.NullPointerException

how can I fix it?

Thank you and Merry Christmas

giga · Dec 24, 2013

FabioG said:

I would like to create a library in order to flash the LED notification so colorful

I wrote this code in Eclips

B4X:

package net.snclab.lednotificationcontrol;

import android.app.Notification;
import android.app.NotificationManager;
import android.content.Context;
import android.graphics.Color;
import anywheresoftware.b4a.BA.Author;
import anywheresoftware.b4a.BA.ShortName;
import anywheresoftware.b4a.BA.Version;

@ShortName("LedNotificationControl")
@Author("FabioG")
@Version(1.0f)


public class LedNotificationControl {

    private Context mContext;

    public void LedFlashColor(int A, int R, int G, int B)
    {
    NotificationManager nm = ( NotificationManager ) mContext.getSystemService(Context.NOTIFICATION_SERVICE);
    Notification notif = new Notification();
    notif.ledARGB = Color.argb(A, R, G, B);
    notif.flags = Notification.FLAG_SHOW_LIGHTS; //Notification.DEFAULT_LIGHTS;
    notif.ledOnMS = 100;
    notif.ledOffMS = 100;
    nm.notify(0, notif);
    }


    public void ClearLED()
    {
    NotificationManager nm = ( NotificationManager ) mContext.getSystemService( Context.NOTIFICATION_SERVICE );
    nm.cancel(0);
    }

}

but when I use it in B4A I get this error

B4X:

java.lang.NullPointerException

how can I fix it?

Thank you and Merry Christmas

Is this the complete error?

FabioG · Dec 25, 2013

giga said:
Is this the complete error?

This error appears when I start the application and execute the command library

FabioG · Dec 25, 2013

it works perfectly

thank you very much

Merry Christmas

Theera · Dec 25, 2013

Hi FabioG,
Do you have a example for bring this library to use? I need to learn more.

FabioG · Dec 25, 2013

Theera said:
Hi FabioG,
Do you have a example for bring this library to use? I need to learn more.

that is only the first part of the library code

I would like to complete it in these days and being able to post in this forum

that code written on it for the moment only works if the activity is started with the screen off, if you turn on the screen and then off the LED stops flashing

giga · Dec 26, 2013

I think the forum will need more of the error code in order to help with this. java.lang.NullPointerException could be caused by any of the following

Per Oracle:

Thrown when an application attempts to use null in a case where an object is required. These include:

Calling the instance method of a null object.
Accessing or modifying the field of a null object.
Taking the length of null as if it were an array.
Accessing or modifying the slots of null as if it were an array.
Throwing null as if it were a Throwable value.

Theera · Dec 26, 2013

I can compile a library by slc, Ihave no error.

stevel05 · Dec 26, 2013

My response has disappeared, I must have deleted it when changing a spelling error.

In FabioG's code mContext is not initialized, I suggested he try:

B4X:

private Context mContext = BA.applicationContext;

Which apparently worked.

Sorry for the deletion.

FabioG · Dec 26, 2013

I have another problem
when call the function StartIconNotify app crash

this is the cose

I can fix ?

B4X:

package net.snclab.lednotificationcontrol;

import android.app.Notification;
import android.app.NotificationManager;

import android.content.Context;
import android.graphics.Color;
import android.support.v4.app.NotificationCompat;
import anywheresoftware.b4a.BA.Author;
import anywheresoftware.b4a.BA.ShortName;
import anywheresoftware.b4a.BA.Version;
import anywheresoftware.b4a.BA;


@ShortName("LedNotificationControl")
@Author("FabioG")
@Version(1.0f)


public class LedNotificationControl {


    private static final String Icon = null;
    private Context mContext = BA.applicationContext;
    NotificationCompat.Builder builder;
   
    NotificationManager nm = ( NotificationManager ) mContext.getSystemService(Context.NOTIFICATION_SERVICE);
    Notification notif = new Notification();
       

    /**
    * A, B, R,G and B is ARGB Colors
    * TimeOutONms is the Timeout for Led On in Milliseconds
    * TimeOutOFFms is the Timeout for Led Off in Milliseconds
    * NOTIFY_ID is the ID for the Notification
    **/
   
    public void LedFlashColor(int A, int R, int G, int B, int TimeOutONms, int TimeOutOFFms, int NOTIFY_ID)   
    {

        notif.ledARGB = Color.argb(A, R, G, B); 
        notif.flags = Notification.FLAG_SHOW_LIGHTS;
        notif.ledOnMS = TimeOutONms; 
        notif.ledOffMS = TimeOutOFFms;

        nm.notify(NOTIFY_ID, notif);
   
       
    }
   
    public void ClearLED(int NOTIFY_ID)
    {
        NotificationManager nm = ( NotificationManager ) mContext.getSystemService( Context.NOTIFICATION_SERVICE );
       
    nm.cancel(NOTIFY_ID);
    }
   
    public void StartIconNotify()
    {
        builder.setContentTitle("Notification")
        .setContentText("ContentText")
        .setTicker("TickerText")
        .setSmallIcon(BA.applicationContext.getResources().getIdentifier(Icon, "drawable", BA.packageName))
        .setWhen(System.currentTimeMillis());
       
        nm.notify(1, builder.build());
       
    }
   
}

stevel05 · Dec 26, 2013

What is the error you are getting?

stevel05 · Dec 26, 2013

I can't see that you've initialized builder!

FabioG · Dec 26, 2013

stevel05 said:
I can't see that you've initialized builder!

this is the error

If use

B4X:

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this)

Eclipse return

B4X:

The constructor NotificationCompat.Builder(LedNotificationControl) is undefined

B4X:

** Activity (main) Create, isFirst = true **
main_activity_create (java line: 283)


java.lang.NoClassDefFoundError: android.support.v4.app.NotificationCompat$Builder


    at net.snclab.lednotificationcontrol.LedNotificationControl.StartIconNotify(LedNotificationControl.java:60)
    at net.snclabs.TestAPP.main._activity_create(main.java:283)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:525)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:170)
    at net.snclabs.TestAPP.main.afterFirstLayout(main.java:98)
    at net.snclabs.TestAPP.main.access$100(main.java:16)
    at net.snclabs.TestAPP.main$WaitForLayout.run(main.java:76)
    at android.os.Handler.handleCallback(Handler.java:730)
    at android.os.Handler.dispatchMessage(Handler.java:92)
    at android.os.Looper.loop(Looper.java:137)
    at android.app.ActivityThread.main(ActivityThread.java:5103)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:525)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
    at dalvik.system.NativeStart.main(Native Method)

stevel05 · Dec 26, 2013

What version of Android have you configured in Tools/configure Paths?

FabioG · Dec 26, 2013

stevel05 said:
What version of Android have you configured in Tools/configure Paths?

api version 19

stevel05 · Dec 26, 2013

The constructor NotificationCompat.Builder(LedNotificationControl) is undefined

The constructor requires a Context again so try:

B4X:

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(BA.applicationContext)

Don't forget that the library will form part of the app in which it's being used which will be it's context when it's running.

FabioG · Dec 26, 2013

Thanks, I tried but the same error: (

stevel05 said:
The constructor requires a Context again so try:

B4X:

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(BA.applicationContext)

Don't forget that the library will form part of the app in which it's being used which will be it's context when it's running.

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