Inflate加载布局文件

From:http://blog.csdn.net/jojoyce/article/details/16844919

一、View.inflate和Layoutinflater.inflate有什么联系么？

它们之间的联系看下代码就一目了然了：

[java]
view plaincopyprint?

/**
* Inflate a view from an XML resource. This convenience method wraps the {@link
* LayoutInflater} class, which provides a full range of options for view inflation.
*
* @param context The Context object for your activity or application.
* @param resource The resource ID to inflate
* @param root A view group that will be the parent. Used to properly inflate the
* layout_* parameters.
* @see LayoutInflater
*/
public static View inflate(Context context, int resource, ViewGroup root) {
LayoutInflater factory = LayoutInflater.from(context);
return factory.inflate(resource, root);
}

/**
* Inflate a view from an XML resource. This convenience method wraps the {@link
* LayoutInflater} class, which provides a full range of options for view inflation.
*
* @param context The Context object for your activity or application.
* @param resource The resource ID to inflate
* @param root A view group that will be the parent. Used to properly inflate the
* layout_* parameters.
* @see LayoutInflater
*/
public static View inflate(Context context, int resource, ViewGroup root) {
LayoutInflater factory = LayoutInflater.from(context);
return factory.inflate(resource, root);
}

二、LayoutInflater中的四个inflate方法的有什么不同？

inflate加载xml文件并不是当你调用inflate方法时去解析一个xml纯文件，而是有一个预编译的过程。



[java]
view plaincopyprint?

public View inflate(int resource, ViewGroup root) {
return inflate(resource, root, root != null);
}
public View inflate(int resource, ViewGroup root, boolean attachToRoot) {
if (DEBUG) System.out.println("INFLATING from resource: " + resource);
XmlResourceParser parser = getContext().getResources().getLayout(resource);
try {
return inflate(parser, root, attachToRoot);
} finally {
parser.close();
}
}
public View inflate(XmlPullParser parser, ViewGroup root) {
return inflate(parser, root, root != null);
}

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

final AttributeSet attrs = Xml.asAttributeSet(parser);
Context lastContext = (Context)mConstructorArgs[0];
mConstructorArgs[0] = mContext;
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, attrs, false);
} else {
// Temp is the root view that was found in the xml

View temp;
if (TAG_1995.equals(name)) {
temp = new BlinkLayout(mContext, attrs);
} else {
temp = createViewFromTag(root, name, 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

rInflate(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) {
InflateException ex = new InflateException(e.getMessage());
ex.initCause(e);
throw ex;
} catch (IOException e) {
InflateException ex = new InflateException(
parser.getPositionDescription()
+ ": " + e.getMessage());
ex.initCause(e);
throw ex;
} finally {
// Don't retain static reference on context.

mConstructorArgs[0] = lastContext;
mConstructorArgs[1] = null;
}

Trace.traceEnd(Trace.TRACE_TAG_VIEW);

return result;
}
}

public View inflate(int resource, ViewGroup root) {
return inflate(resource, root, root != null);
}
public View inflate(int resource, ViewGroup root, boolean attachToRoot) {
if (DEBUG) System.out.println("INFLATING from resource: " + resource);
XmlResourceParser parser = getContext().getResources().getLayout(resource);
try {
return inflate(parser, root, attachToRoot);
} finally {
parser.close();
}
}
public View inflate(XmlPullParser parser, ViewGroup root) {
return inflate(parser, root, root != null);
}

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

final AttributeSet attrs = Xml.asAttributeSet(parser);
Context lastContext = (Context)mConstructorArgs[0];
mConstructorArgs[0] = mContext;
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, attrs, false);
} else {
// Temp is the root view that was found in the xml
View temp;
if (TAG_1995.equals(name)) {
temp = new BlinkLayout(mContext, attrs);
} else {
temp = createViewFromTag(root, name, 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
rInflate(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) {
InflateException ex = new InflateException(e.getMessage());
ex.initCause(e);
throw ex;
} catch (IOException e) {
InflateException ex = new InflateException(
parser.getPositionDescription()
+ ": " + e.getMessage());
ex.initCause(e);
throw ex;
} finally {
// Don't retain static reference on context.
mConstructorArgs[0] = lastContext;
mConstructorArgs[1] = null;
}

Trace.traceEnd(Trace.TRACE_TAG_VIEW);

return result;
}
}

这篇博客是深入分析一个View的创建过程，博主分析得很透彻：/article/6933333.html

三、inflate()中各个参数代表什么？

[java]
view plaincopyprint?

public View inflate(int resource, ViewGroup root) {
return inflate(resource, root, root != null);
}
public View inflate(int resource, ViewGroup root, boolean attachToRoot)
resource参数很好理解，可能不好理解就是root和attachToRoot两个参数，通过分析源码我们可以知道：
View result = root;
View temp;
if (TAG_1995.equals(name)) {
temp = new BlinkLayout(mContext, attrs);
} else {
temp = createViewFromTag(root, name, attrs);
}
if (root == null || !attachToRoot) {
result = temp;
}
if (root != null && attachToRoot) {
root.addView(temp, params);
}
return result;

public View inflate(int resource, ViewGroup root) {
return inflate(resource, root, root != null);
}
public View inflate(int resource, ViewGroup root, boolean attachToRoot)
resource参数很好理解，可能不好理解就是root和attachToRoot两个参数，通过分析源码我们可以知道：
View result = root;
View temp;
if (TAG_1995.equals(name)) {
temp = new BlinkLayout(mContext, attrs);
} else {
temp = createViewFromTag(root, name, attrs);
}
if (root == null || !attachToRoot) {
result = temp;
}
if (root != null && attachToRoot) {
root.addView(temp, params);
}
return result;

也就是说：假如root设置为null或者root!=nul但attachToRoot设置为false，则这个xml加载出来的view不会挂载到别的视图节点上去；
当root!=null并且attachToRoot设置为true时，就会挂载上去，return为root
当root!=nul但attachToRoot设置为false时，这个root用来view生成正确的params布局参数来match root。

[java]
view plaincopyprint?

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);
}
}