[Android]AddView error [The specified child already has a parent. You must call removeView() on the child's parent first.]

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Hi,

I have a problem in View in Android. I tried to resume my apps after Home Key interrupt and changed language, but this error occured :
The specified child already has a parent. You must call removeView() on the child's parent first.

I already google it, and all answer said that : I need to removeView on parent or create new instance of view for this.

Here's my code (which error on "The specified child already has a parent.....")

Java

 public void CreateVeiw()
{
        super.createView();
		
        mFrameLayout.removeViewInLayout(m_sInstance.m_view);
	mView.addView(m_FakeEditTextBox);
	mFrameLayout.addView(m_sInstance.m_view);
	setContentView(mFrameLayout);
		....
                .....

and I changed it to this :

Java

 public void CreateVeiw()
{
        super.createView();
		
        mFrameLayout.removeViewInLayout(m_sInstance.m_view);
	mView.removeView(m_FakeEditTextBox);  // I added this
        m_FakeEditTextBox = new FakeEditText(this); // I added this
	mView.addView(m_FakeEditTextBox);
	mFrameLayout.addView(m_sInstance.m_view);
	setContentView(mFrameLayout);
		....
                .....

The previous error is not occurs, but there's new error. It's say :

Java

NullPointerException

when I tried to call

Java

mFrameLayout

Anyone can help me?

Thanks a lot

Posted 11-Sep-13 18:02pm

satrio_budidharmawan

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-09-11T19:09:00

I'm sure, you did not correctly point out the line where the exception is thrown. First of all, you could not "call mFrameLayout", as this is an object, not a method. And you did not show what method you have called. Anyway, this object itself cannot be null, otherwise it would throw the same exception in first code sample, but it wasn't the case (unless you changed something else, but it would contradict your description of the problem). Next time, run it under the debugger and comment the lines where some exception is thrown.

Not to worry. This is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferenced by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: either make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else.

Please see also: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object"[^].

Sometimes, you cannot do it under debugger, by one or another reason. One really nasty case is when the problem is only manifested if software is built when debug information is not available. In this case, you have to use the harder way. First, you need to make sure that you never block propagation of exceptions by handling them silently (this is a crime of developers against themselves, yet very usual). The you need to catch absolutely all exceptions on the very top stack frame of each thread. You can do it if you handle the exceptions of the type System.Exception. In the handler, you need to log all the exception information, especially the System.Exception.StackTrace:
http://msdn.microsoft.com/en-us/library/system.exception.aspx[^],
http://msdn.microsoft.com/en-us/library/system.exception.stacktrace.aspx[^].

The stack trace is just a string showing the full path of exception propagation from the throw statement to the handler. By reading it, you can always find ends. For logging, it's the best (in most cases) to use the class System.Diagnostics.EventLog:
http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx[^].

However, in this very case, you should not try to use RemoveView. Instead, you should find and fix your bug in first place, which seems to be very simple: m_FakeEditTextBox already has a parent, so it was already added to some view. Find where it was added and remove that line.

Good luck,

—SA