Activity setContentView流程
分析setContentView流程
frameworks/base/core/java/android/app/Activity.java路径下找到入口
public void setContentView(int layoutResID) {
getWindow().setContentView(layoutResID);
initActionBar();
}Activity又调用了mWindow中的setContentView
public Window getWindow() {
return mWindow;
}看看mWindow是什么东西,attach方法中找到了mWindow的初始化
final void attach(Context context, ActivityThread aThread,
Instrumentation instr, IBinder token, int ident,
Application application, Intent intent, ActivityInfo info,
CharSequence title, Activity parent, String id,
NonConfigurationInstances lastNonConfigurationInstances,
Configuration config) {
//...
mWindow = PolicyManager.makeNewWindow(this);
//...
}frameworks/base/core/java/com/android/internal/policy/PolicyManager.java
跟着来到PolicyManager这个类中
public final class PolicyManager {
//需要反射创建出来的对象
private static final String POLICY_IMPL_CLASS_NAME =
"com.android.internal.policy.impl.Policy";
private static final IPolicy sPolicy;
static {
//...
Class policyClass = Class.forName(POLICY_IMPL_CLASS_NAME);
sPolicy = (IPolicy)policyClass.newInstance();
//...
}
//...
//我们的mWindow对象又是调用了sPolicy.makeNewWindow(context)，所以继续跟
public static Window makeNewWindow(Context context) {
return sPolicy.makeNewWindow(context);
}
//...
}通过上面的代码能知道sPolicy.makeNewWindow(context)这个接口调用的方法实现类是
com.android.internal.policy.impl.Policy，我们去找。
frameworks/base/policy/src/com/android/internal/policy/impl/Policy.java
public class Policy implements IPolicy {
//...
//终于知道了 mWindow 的对象是PhoneWindow实现的.
public Window makeNewWindow(Context context) {
return new PhoneWindow(context);
}
//...
}
好，到了这里终于知道Activity中的getWindow()对象就是PhoneWindow，那么继续去查找PhoneWindow中的setContentView
frameworks/base/policy/src/com/android/internal/policy/impl/PhoneWindow.java
public class PhoneWindow extends Window implements MenuBuilder.Callback {
private LayoutInflater mLayoutInflater;
//...
@Override
public void setContentView(int layoutResID) {
if (mContentParent == null) {
installDecor();
} else {
mContentParent.removeAllViews();
}
//我们设置的activity_main.xml布局传到了这里，继续跟过去看看
mLayoutInflater.inflate(layoutResID, mContentParent);
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
}
//...
}到了这里知道我们平时设置的activity_main.xml被传入了 mLayoutInflater.inflate(layoutResID, mContentParent);方法中，路径是：
frameworks/base/core/java/android/view/LayoutInflater.java
public abstract class LayoutInflater {
//...
//调用了下面的方法
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);
//获取xml解析器
XmlResourceParser parser = getContext().getResources().getLayout(resource);
try {
return inflate(parser, root, attachToRoot);
} finally {
parser.close();
}
}
//...
}
通过上面代码找到了Xml的解析器是 .getLayout(resource); 返回的，来看看代码
frameworks/base/core/java/android/content/res/Resources.java
public class Resources {
//...
final AssetManager mAssets;
//...
public XmlResourceParser getLayout(int id) throws NotFoundException {
return loadXmlResourceParser(id, "layout");
}
//...
//我们的activity_main.xml传到了这里
XmlResourceParser loadXmlResourceParser(int id, String type)
throws NotFoundException {
synchronized (mTmpValue) {
TypedValue value = mTmpValue;
getValue(id, value, true);
if (value.type == TypedValue.TYPE_STRING) {
return loadXmlResourceParser(value.string.toString(), id,
value.assetCookie, type);
}
//...
}
}
//...
//activity_main.xml又传到了getValue当中
public void getValue(int id, TypedValue outValue, boolean resolveRefs)
throws NotFoundException {
//AssetManager 对象中的 getResourceValue
boolean found = mAssets.getResourceValue(id, 0, outValue, resolveRefs);
if (found) {
return;
}
throw new NotFoundException("Resource ID #0x"
+ Integer.toHexString(id));
}
//...
}frameworks/base/core/java/android/content/res/AssetManager.java
AssetManager 里的native方法不知道怎么调用的，没找到动态库加载，记录一下。
public final class AssetManager {
//...
/*package*/ final boolean getResourceValue(int ident,
int density,
TypedValue outValue,
boolean resolveRefs)
{
//这是一个本地方法,去获取资源的block，其实是以个index
int block = loadResourceValue(ident, (short) density, outValue, resolveRefs);
if (block >= 0) {
if (outValue.type != TypedValue.TYPE_STRING) {
return true;
}
//给TyepValue 根据id获取string
outValue.string = mStringBlocks[block].get(outValue.data);
return true;
}
return false;
}
//...
}
回到frameworks/base/core/java/android/view/LayoutInflater.java
中去查看return inflate(parser, root, attachToRoot);这个方法。
public abstract class LayoutInflater {
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, boolean attachToRoot) {
synchronized (mConstructorArgs) {
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("到这里就知道整个xml里面的控件是怎么通过解析后拿到name以后进行反射出来了。