[Android] AddView错误[指定的子级已经有父级。您必须首先在孩子的父母上调用removeView（）。]

问题描述：

我在Android中的View中遇到了问题。我试图在Home Key中断和更改语言后恢复我的应用程序，但发生此错误：

指定的孩子已经有父母。你必须先在孩子的父母身上调用removeView（）。

我已经谷歌了，所有的答案都说：我需要删除父母或为此创建新的视图实例。

这是我的代码（关于指定的孩子已经有父母......的错误）

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.....")

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

我将其更改为：

and I changed it to this :

 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);
		....
                .....

之前的错误没有发生，但有新的错误。它说：

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

NullPointerException

当我试图调用

mFrameLayout

任何人都可以帮助我吗？

非常感谢

Anyone can help me?

Thanks a lot

答

我是当然，您没有正确指出引发异常的行。首先，你不能调用 mFrameLayout ，因为这是一个对象，而不是方法。你没有表明你所谓的方法。无论如何，这个对象本身不能为null，否则它会在第一个代码示例中抛出相同的异常，但事实并非如此（除非你改变了其他东西，但它会与你对问题的描述相矛盾）。下次，在调试器下运行它，注释抛出一些异常的行。

不用担心。这是检测和修复的最简单的案例之一。它只是意味着某些引用类型的某个成员/变量通过使用和它的实例（非静态）成员解除引用，这要求此成员/变量为非null，但实际上它似乎为null。只需在调试器下执行它，它将停止抛出异常的执行。在该行上设置一个断点，重新启动应用程序并再次到达这一点。评估下一行中涉及的所有引用，并查看哪一个为null，而不需要为null。解决这个问题之后，修复代码：要么确保将成员/变量正确初始化为非空引用，要么将其检查为null，如果为null，则执行其他操作。

另请参阅：想要在按钮点击时显示下一条记录。但是如果下一条记录功能的条件对象引用没有设置为对象的实例 [ ^ ]。

有时候，你不能在调试器下，由于一个或另一个原因做到这一点。一个非常讨厌的情况是，只有在调试信息不可用时构建软件时才会出现问题。在这种情况下，你必须使用更难的方式。首先，你需要确保你永远不会通过静默处理异常来阻止异常的传播（这是开发人员对自己的犯罪，但很常见）。您需要在每个线程的最顶层堆栈帧上捕获绝对所有异常。如果处理类型 System.Exception 的异常，则可以执行此操作。在处理程序中，您需要记录所有异常信息，尤其是 System.Exception.StackTrace ：

http://msdn.microsoft.com/en-us/library/system.exception.aspx [ ^ ]，

http://msdn.microsoft.com/en-us/library/system.exception。 stacktrace.aspx [ ^ ]。

堆栈跟踪只是一个字符串，显示从throw语句到处理程序的异常传播的完整路径。通过阅读，您总能找到目的。对于日志记录，使用类 System.Diagnostics.EventLog ：

http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx [ ^ ]。

但是，在这种情况下，你不应该尝试使用 RemoveView 。相反，你应该首先找到并修复你的bug，这似乎很简单： m_FakeEditTextBox 已经有一个父，所以它已经被添加到某个视图中了。找到它的添加位置并删除该行。

祝你好运，

-SA

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

[Android] AddView错误[指定的子级已经有父级。您必须首先在孩子的父母上调用removeView（）。]

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