Java Question Problem with Java Code / Library

F

FabioG

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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
 
Last edited:
giga

giga

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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
Click to expand...

Is this the complete error?
 
Theera

Theera

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

FabioG

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

giga

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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

Theera

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I can compile a library by slc, Ihave no error.
 
stevel05

stevel05

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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.
 
F

FabioG

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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

stevel05

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What is the error you are getting?
 
stevel05

stevel05

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

FabioG

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stevel05 said:
I can't see that you've initialized builder!
Click to expand...

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)
 
Last edited:
stevel05

stevel05

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

stevel05

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The constructor NotificationCompat.Builder(LedNotificationControl) is undefined
Click to expand...

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.
 
F

FabioG

Active Member
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Longtime User
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.
Click to expand...
 
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