The specified child already has a parent..."错误

当我们调用ViewGroup的addView()方法时

public void addView(View child) {

        addView(child, -1);

}

最终会调用addViewInLayout()方法

private void addViewInner(View child, int index, LayoutParams params,            boolean preventRequestLayout) {        if (mTransition != null) {            // Don't prevent other add transitions from completing, but cancel remove            // transitions to let them complete the process before we add to the container            mTransition.cancel(LayoutTransition.DISAPPEARING);        }        if (child.getParent() != null) {            throw new IllegalStateException("The specified child already has a parent. " +                    "You must call removeView() on the child's parent first.");        }        ...        if (index < 0) {            index = mChildrenCount;        }   ...}  

由此可知，产生这个错误的原因是child.getParent() != null,即当前View的parent不为空，之前有被加到过ViewGroup里面

解决办法:调用父view的removeAllViews()或者removeView()方法。如果不知道父view，可以使用这个方法

<pre name="code" class="java">public static void removeParent(View v){        ViewParent parent = v.getParent();        if(parent instanceof ViewGroup){            ViewGroup group=(ViewGroup) parent;            group.removeView(v);        }    }