Java Question Error creating a library

[aviario]

Hello.

First of all sorry for my bad english.
Second. I haven't idea of Java, but I'm searching documentation on google and forums.

I'm trying to create a library in eclipse to print image on esc /p printers. I found code to do this in java, and I used Eclipse to generate jar and javadoc.

I import the jar into b4a, and i can access to procedures of the library. But When I run b4a code i have the next error:

PackageAdded: package:b4a.example
main_globals (java line: 273)
java.lang.NoClassDefFoundError: sico.PosPrinter.PosPrinterClass
at b4a.example.main._globals(main.java:273)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:169)
at b4a.example.main.initializeGlobals(main.java:230)
at b4a.example.main.afterFirstLayout(main.java:86)
at b4a.example.main.access$100(main.java:16)
at b4a.example.main$WaitForLayout.run(main.java:74)
at android.os.Handler.handleCallback(Handler.java:605)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4424)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:558)
at dalvik.system.NativeStart.main(Native Method)

I read a lot in google, but i don't undestand.

Here are the library.

In the zip isn't android.jar, B4AShared.jar and Core.jar, that i have in a libs folder inside Posprinter folder, because the forun don't let me upload files up to 512kb.

Can you help me?

Thanks.

 

[Erel]

How are you creating the jar file? Are you using SLC tool?

 

[socialnetis]

I have seen 2 ways of getting a NoClassDefFoundError:
- When wrapping a java library, you need to add the "@DependsOn" notation, an put the name of the library you are wrapping. Which I assume is not the case, because there are not imports to any external library related to a printer in the code you provided
- Compiling in eclipse using JDK 1.7, you need to use 1.6

 

[aviario]

Hello. Tranks for reply.
I created jar with eclipse, with the option to export.
first I compiling using JDK 1.7. But I read in foruns that I need to use 1.6. Then I change in Java Paths, Jdk 1.7 for 1.6 but Isn't work.
the only libraries that i use are android.jar, B4AShared.jar and Core.jar, and of course Jdk 1.6

I read something abaout classpath, but I don't undestand it. I try to add android.jar, B4AShared.jar and Core.jar into jar created, into a folder named libs. But isn't work.

When I add library to b4a is ok, but when compiling project crash.

Thanks again for you replies.

 

[Erel]

You shouldn't add those jars. Only reference them in your project. Try to use SLC tool. You can use it together with eclipse.

In your case you do not need to copy any file to the libs folder.

 

[aviario]

Thanks for reply.

I use SLC Tool and solve the error java.lang.NoClassDefFoundError: sico.PosPrinter.PosPrinterClass

Now I have the next error

java.lang.NullPointerException
at android.widget.Toast.<init>(Toast.java:92)
at android.widget.Toast.makeText(Toast.java:233)
at sico.PosPrinter.PosPrinterClass.print_image(PosPrinterClass.java:74)
at b4a.example.main._activity_create(main.java:238)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at anywheresoftware.b4a.BA.raiseEvent2(BA.java:169)
at b4a.example.main.afterFirstLayout(main.java:89)
at b4a.example.main.access$100(main.java:16)
at b4a.example.main$WaitForLayout.run(main.java:74)
at android.os.Handler.handleCallback(Handler.java:605)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4424)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:558)
at dalvik.system.NativeStart.main(Native Method)
java.lang.NullPointerException

I supose the error occurs because I Inicialize some var as null and i can't do it. Meaby the error is in toast line.

I use Toast.makeText(mContexto, "Fichero no Existe", Toast.LENGTH_SHORT)
because I can't do it Toast.makeText(this, "Fichero no Existe", Toast.LENGTH_SHORT), because i haven't activity.

Then I create a mContext as Activity an inicialized to null:

import android.widget.Toast;
import android.app.Activity;

Activity mContexto = null;
......
Toast.makeText(mContexto, "Fichero no Existe", Toast.LENGTH_SHORT)

but I don't konw if this is ok.

Thansk again

 

[Erel]

It is not ok. You should add a BA parameter to your method. You can then get the context with ba.context.