Java Question Getting the class of a activity.

barx · Mar 6, 2013

Trying to build a Notification Builder lib and have come across a little problem.

When trying to create a false backstack, you use a line something like

B4X:

stackBuilder.addParentStack(ResultActivity.class);

As you can see a class is passed as arg0

How can I pass a b4a activity object and get it's class for this line?

Thanks

Erel · Mar 7, 2013

Something like:

B4X:

public void YourMethod(BA ba, other parameters...) {
 stackBuilder.addParentStack(ba.activity.getClass());
}

barx · Mar 7, 2013

I tried something similar and get an error.

Basically i have a method called setParentActivity and pass a b4a activity as an Object and assign it it to an Object called pActivity

B4X:

nb.setParentActivity(main2)

then in lib I have

B4X:

stackBuilder.addParentStack(pActivity.getClass());

After I compile the b4a test project I get an error in the log

B4X:

** Activity (main) Create, isFirst = true **


Class returned class java.lang.Class


main_activity_create (java line: 248)
java.lang.IllegalArgumentException: android.content.pm.PackageManager$NameNotFoundException: ComponentInfo{barxdroid.nbtest/java.lang.Class}


   at android.support.v4.app.TaskStackBuilder.addParentStack(TaskStackBuilder.java:197)
   at barxdroid.NotificationBuilder.NotificationBuilder.Notify(NotificationBuilder.java:116)
   at barxdroid.nbtest.main._activity_create(main.java:248)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:511)
   at anywheresoftware.b4a.BA.raiseEvent2(BA.java:167)
   at barxdroid.nbtest.main.afterFirstLayout(main.java:85)
   at barxdroid.nbtest.main.access$100(main.java:16)
   at barxdroid.nbtest.main$WaitForLayout.run(main.java:72)
   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:4575)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:511)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
   at dalvik.system.NativeStart.main(Native Method)
Caused by: android.content.pm.PackageManager$NameNotFoundException: ComponentInfo{barxdroid.nbtest/java.lang.Class}
   at android.app.ApplicationPackageManager.getActivityInfo(ApplicationPackageManager.java:223)
   at android.support.v4.app.NavUtils.getParentActivityName(NavUtils.java:264)
   at android.support.v4.app.NavUtils.getParentActivityIntent(NavUtils.java:211)
   at android.support.v4.app.TaskStackBuilder.addParentStack(TaskStackBuilder.java:190)
   ... 17 more
java.lang.IllegalArgumentException: android.content.pm.PackageManager$NameNotFoundException: ComponentInfo{barxdroid.nbtest/java.lang.Class}

I have also tried creating a testing method to that does

B4X:

return pActivity.getClass().toString();

And all it ever seems to return is 'java.lang.Class'

Puzzled!

barx · Mar 7, 2013

Just tested for curiosity sake with

B4X:

stackBuilder.addParentStack(ba.activity.getClass());

And get a NullPointerException

B4X:

** Activity (main) Create, isFirst = true **


main_activity_create (java line: 246)


java.lang.NullPointerException
   at barxdroid.NotificationBuilder.NotificationBuilder.Notify(NotificationBuilder.java:116)
   at barxdroid.nbtest.main._activity_create(main.java:246)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:511)
   at anywheresoftware.b4a.BA.raiseEvent2(BA.java:167)
   at barxdroid.nbtest.main.afterFirstLayout(main.java:85)
   at barxdroid.nbtest.main.access$100(main.java:16)
   at barxdroid.nbtest.main$WaitForLayout.run(main.java:72)
   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:4575)
   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:789)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
   at dalvik.system.NativeStart.main(Native Method)
java.lang.NullPointerException

barx · Mar 7, 2013

The confusing thing is the Object is checked for Null before hand this is the code used.

B4X:

   if(nActivity != null) {
         Intent resultIntent = new Intent(Common.getComponentIntent(ba, nActivity));
         if(pActivity != null) {
            TaskStackBuilder stackBuilder = TaskStackBuilder.create(ba.context);
            stackBuilder.addParentStack(pActivity.getClass());
            stackBuilder.addNextIntent(resultIntent);
            PendingIntent resultPendingIntent = stackBuilder.getPendingIntent(0, PendingIntent.FLAG_UPDATE_CURRENT);
            ((Builder)getObject()).setContentIntent(resultPendingIntent);
         }
      }

So I guess the Object exists but the getClass() isn't doing what is required.

Erel · Mar 8, 2013

The problem is not in getClass().

agraham · Mar 8, 2013

barx said:
And all it ever seems to return is 'java.lang.Class'

That's expected behaviour. Try getClass().getName() to see the actual class.

barx · Mar 9, 2013

Indeed the NullPointException wasn't to do with the getClass().

But now I get a IllegalState error. Will get the exact error later when I am back home.

barx · Mar 9, 2013

Just run the code and this line

B4X:

stackBuilder.addParentStack(pActivity.getClass());

Causes this error in log

B4X:

LogCat connected to: SH0BCRT05610
--------- beginning of /dev/log/system


--------- beginning of /dev/log/main


** Activity (main) Create, isFirst = true **


java.lang.Class
main_activity_create (java line: 250)
java.lang.IllegalArgumentException: android.content.pm.PackageManager$NameNotFoundException: ComponentInfo{barxdroid.nbtest/java.lang.Class}
   at android.support.v4.app.TaskStackBuilder.addParentStack(TaskStackBuilder.java:197)
   at barxdroid.NotificationBuilder.NotificationBuilder.Notify(NotificationBuilder.java:195)
   at barxdroid.nbtest.main._activity_create(main.java:250)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:511)
   at anywheresoftware.b4a.BA.raiseEvent2(BA.java:167)
   at barxdroid.nbtest.main.afterFirstLayout(main.java:85)
   at barxdroid.nbtest.main.access$100(main.java:16)
   at barxdroid.nbtest.main$WaitForLayout.run(main.java:72)
   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:4575)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:511)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
   at dalvik.system.NativeStart.main(Native Method)
Caused by: android.content.pm.PackageManager$NameNotFoundException: ComponentInfo{barxdroid.nbtest/java.lang.Class}
   at android.app.ApplicationPackageManager.getActivityInfo(ApplicationPackageManager.java:223)
   at android.support.v4.app.NavUtils.getParentActivityName(NavUtils.java:264)
   at android.support.v4.app.NavUtils.getParentActivityIntent(NavUtils.java:211)
   at android.support.v4.app.TaskStackBuilder.addParentStack(TaskStackBuilder.java:190)
   ... 17 more
java.lang.IllegalArgumentException: android.content.pm.PackageManager$NameNotFoundException: ComponentInfo{barxdroid.nbtest/java.lang.Class}

Any Ideas?

the 'java.lang.Class in the log just before the Main_Activity_Create is what is returned from

B4X:

BA.Log(pActivity.getClass().getName());

Thanks

agraham · Mar 9, 2013

This is a wild guess and you may have tried this already! The Android docs for TaskStackBuilder.addParentStack(Class<?> sourceActivityClass) say

Add the activity parent chain as specified by manifest <meta-data> elements to the task stack builder.

It's typically obtuse (I find the Android documentation is usually totally unhelpful) but the standard Basic4android manifest doesn't seem to have a <meta-data> tag so maybe it's complaining about the lack of a name attribute in the meta-data.

Informatix · Mar 9, 2013

Here's something you can try. I get no error with this code (ActModName is the activity module name as it appears in B4A, e.g. "Main" for the main activity):

B4X:

public void Test(BA ba, String ActModName)
{
   String PN = BA.packageName;
   TaskStackBuilder stackBuilder = TaskStackBuilder.create(ba.context);
   stackBuilder.addParentStack(new ComponentName(PN, PN + "." + ActModName.toLowerCase(BA.cul)));
}

barx · Mar 9, 2013

agraham said:
This is a wild guess and you may have tried this already! The Android docs for TaskStackBuilder.addParentStack(Class<?> sourceActivityClass) say
It's typically obtuse (I find the Android documentation is usually totally unhelpful) but the standard Basic4android manifest doesn't seem to have a <meta-data> tag so maybe it's complaining about the lack of a name attribute in the meta-data.

I foreseen this as a possible issues, hence this post

http://www.b4x.com/forum/basic4android-updates-questions/27094-manifest-editor-add-meta-data.html

Thanks for the pointer though agraham, it all helps

barx · Mar 9, 2013

Informatix said:
Here's something you can try. I get no error with this code (ActModName is the activity module name as it appears in B4A, e.g. "Main" for the main activity):

B4X:

public void Test(BA ba, String ActModName) { String PN = BA.packageName; TaskStackBuilder stackBuilder = TaskStackBuilder.create(ba.context); stackBuilder.addParentStack(new ComponentName(PN, PN + "." + ActModName.toLowerCase(BA.cul))); }

Will give it a try Informatix and report back thanks.

barx · Mar 9, 2013

Reporting back as promised.

Added the code you posted Informatix and got an NoSucgMethodError.

Logged the .tostring of the ComponentName and it was returning

B4X:

ComponentInfo{barxdroid.nbtest/barxdroid.nbtest.main2}

So I tried tweaking the code to

B4X:

ComponentName cn = new ComponentName(pn, "." + pActivity.toLowerCase((BA.cul)));

Sill get the same error but as you can see from the log, the name now looks right.

B4X:

** Activity (main) Create, isFirst = true **


-3


java.lang.String


ComponentInfo{barxdroid.nbtest/.main2}
main_activity_create (java line: 250)
java.lang.NoSuchMethodError: android.support.v4.app.TaskStackBuilder.addParentStack


   at barxdroid.NotificationBuilder.NotificationBuilder.Notify(NotificationBuilder.java:201)
   at barxdroid.nbtest.main._activity_create(main.java:250)
   at java.lang.reflect.Method.invokeNative(Native Method)
   at java.lang.reflect.Method.invoke(Method.java:511)
   at anywheresoftware.b4a.BA.raiseEvent2(BA.java:167)
   at barxdroid.nbtest.main.afterFirstLayout(main.java:85)
   at barxdroid.nbtest.main.access$100(main.java:16)
   at barxdroid.nbtest.main$WaitForLayout.run(main.java:72)
   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:4575)
   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:789)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
   at dalvik.system.NativeStart.main(Native Method)

barx · Mar 9, 2013

agraham said:
That's expected behaviour. Try getClass().getName() to see the actual class.

Cannot use .getName() for this as it returns a string. Needs to be

B4X:

stackBuilder.addParentStack(resultActivity.class);

not

B4X:

stackBuilder.addParentStack("resultActivity.class");

Any other ideas guys, tried loads of things, just not the right one lol

agraham · Mar 9, 2013

barx said:
Cannot use .getName() for this as it returns a string.

I didn't think you could use it, I assumed that you just wanted a way to confirm that the object that you were trying to use was of the correct Class.

Informatix · Mar 9, 2013

barx said:
Reporting back as promised.

Added the code you posted Informatix and got an NoSucgMethodError.

You have a problem with the support library. "NoSuchMethodError" means the library does not contain a method "addParentStack", but the documentation and my own test prove that it is a method of TaskStackBuilder, without any doubt, and it is included in the support library. So you have a problem with your library. You should get the latest version.

barx said:
So I tried tweaking the code to

B4X:

ComponentName cn = new ComponentName(pn, "." + pActivity.toLowerCase((BA.cul)));

Sill get the same error but as you can see from the log, the name now looks right.

No, it looks wrong. The right name is the one you got first.

barx · Mar 9, 2013

Informatix said:
You have a problem with the support library. "NoSuchMethodError" means the library does not contain a method "addParentStack", but the documentation and my own test prove that it is a method of TaskStackBuilder, without any doubt, and it is included in the support library. So you have a problem with your library. You should get the latest version.

No, it looks wrong. The right name is the one you got first.

Are you saying there is a problem with the support library file I am using?

it is the one included in latest SDK. The addParentStack method comes up (and was selected) from the auto-complete in eclipse. So, you saying I should try and download another copy from somewhere?

Thanks

Informatix · Mar 9, 2013

barx said:
Are you saying there is a problem with the support library file I am using?

it is the one included in latest SDK. The addParentStack method comes up (and was selected) from the auto-complete in eclipse. So, you saying I should try and download another copy from somewhere?

Thanks

1) Did you add DependsOn in your Java code for the support lib ?
2) What version do you have in your B4A libraries folder ?

barx · Mar 9, 2013

1) yes I have

B4X:

@DependsOn(values = {"android-support-v4"})

2) I don't any version in my b4a libs folder.

edit: well at least I didn't think I did until I just tried to copy it over...

Java Question Getting the class of a activity.

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