Android Bugs——RecyclerView.Adapter java.lang.IllegalStateException: The specified child already has

Error：

java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child’s parent first.

原因：

这个问题的原因很简单，该异常表示已经存在父布局，不能再添加父布局。导致该异常的代码可能是：

View view = LayoutInflater.from(getContext()).inflate(R.layout.news_item, parent);

解决方法：

在 inflate() 方法上加入第三个参数，指定为 false 即可。

通常情况下，我们在获取View的时候一般代码都是：

View view = LayoutInflater.from(getContext()).inflate(R.layout.news_item, parent，false);

注意第三个参数为false，所以在获取View的时候并不会把parent设置为View的父布局。默认情况下，如果你不设置inflate的第三个参数，这个参数默认为parent！=null的值。

源码如下：

public View inflate(@LayoutRes int resource, @Nullable ViewGroup root) {
return inflate(resource, root, root != null);
}

public View inflate(XmlPullParser parser, @Nullable ViewGroup root, boolean attachToRoot) {
synchronized (mConstructorArgs) {
Trace.traceBegin(Trace.TRACE_TAG_VIEW, "inflate");

final Context inflaterContext = mContext;
final AttributeSet attrs = Xml.asAttributeSet(parser);
Context lastContext = (Context) mConstructorArgs[0];
mConstructorArgs[0] = inflaterContext;
View result = root;

try {
// Look for the root node.
int type;
while ((type = parser.next()) != XmlPullParser.START_TAG &&
type != XmlPullParser.END_DOCUMENT) {
// Empty
}

if (type != XmlPullParser.START_TAG) {
throw new InflateException(parser.getPositionDescription()
+ ": No start tag found!");
}

final String name = parser.getName();

if (DEBUG) {
System.out.println("**************************");
System.out.println("Creating root view: "
+ name);
System.out.println("**************************");
}

if (TAG_MERGE.equals(name)) {
if (root == null || !attachToRoot) {
throw new InflateException("<merge /> can be used only with a valid "
+ "ViewGroup root and attachToRoot=true");
}

rInflate(parser, root, inflaterContext, attrs, false);
} else {
// Temp is the root view that was found in the xml
final View temp = createViewFromTag(root, name, inflaterContext, attrs);

ViewGroup.LayoutParams params = null;

if (root != null) {
if (DEBUG) {
System.out.println("Creating params from root: " +
root);
}
// Create layout params that match root, if supplied
params = root.generateLayoutParams(attrs);
if (!attachToRoot) {
// Set the layout params for temp if we are not
// attaching. (If we are, we use addView, below)
temp.setLayoutParams(params);
}
}

if (DEBUG) {
System.out.println("-----> start inflating children");
}

// Inflate all children under temp against its context.
rInflateChildren(parser, temp, attrs, true);

if (DEBUG) {
System.out.println("-----> done inflating children");
}

// We are supposed to attach all the views we found (int temp)
// to root. Do that now.
if (root != null && attachToRoot) {
root.addView(temp, params);
}

// Decide whether to return the root that was passed in or the
// top view found in xml.
if (root == null || !attachToRoot) {
result = temp;
}
}

} catch (XmlPullParserException e) {
final InflateException ie = new InflateException(e.getMessage(), e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} catch (Exception e) {
final InflateException ie = new InflateException(parser.getPositionDescription()
+ ": " + e.getMessage(), e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} finally {
// Don't retain static reference on context.
mConstructorArgs[0] = lastContext;
mConstructorArgs[1] = null;

Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}

return result;
}
}

相信读完源码，大家 就会对这个异常晃人大悟了。