decorView和window之间的层级及关系
转载请注明出处：http://blog.csdn.net/guxiao1201/article/details/41744107
首先贴出实现Activity对话框圆角的核心代码
@Override
public void onAttachedToWindow() {
super.onAttachedToWindow();
DisplayMetrics dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);
View view = getWindow().getDecorView();
WindowManager.LayoutParams lp = (WindowManager.LayoutParams)view.getLayoutParams();
lp.gravity = Gravity.CENTER;
lp.width = (dm.widthPixels * 4) / 5;
lp.height = (dm.widthPixels * 4) / 5;
getWindowManager().updateViewLayout(view,lp);
getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
view.setBackgroundResource(R.drawable.dialog_activity_bg);
}通过文章开始贴出的代码View view = getWindow().getDecorView();就可以对Window和DecorView的层级关键猜测一二，decorView是否作为一个变量由window维护？
和之前思路一样，想探究这个问题就得看源码说话。这里依然参考老罗的博客Android应用程序窗口（Activity）的视图对象（View）的创建过程分析。
既然猜测decorView是window的变量，那么就先找到window和activity之间的关系。通过源码发现
public class Activity extends ContextThemeWrapper
implements LayoutInflater.Factory,
Window.Callback, KeyEvent.Callback,
OnCreateContextMenuListener, ComponentCallbacks {
......
private Window mWindow;
......
public Window getWindow() {
return mWindow;
}
......
public void setContentView(int layoutResID) {
getWindow().setContentView(layoutResID);
}
......
} Abstract base class for a top-level window look and behavior policy. An instance of this class should be used as the top-level view added to the window manager. It provides standard UI policies such as a background, title area, default key processing, etc.
The only existing implementation of this abstract class is android.policy.PhoneWindow, which you should instantiate when needing a Window. Eventually that class will be refactored and a factory method added for creating Window instances without knowing about a particular implementation.
Google说Window是WindowManager最顶层的视图，它负责背景(窗口背景)、Title之类的标准的UI元素，Window是一个抽象类，整个Android系统中PhoneWindow是Winodw的唯一实现类。所以接下来进入PhoneWinodw一探究竟。public class PhoneWindow extends Window implements MenuBuilder.Callback {
......
// This is the top-level view of the window, containing the window decor.
private DecorView mDecor;
......
// This is the view in which the window contents are placed. It is either
// mDecor itself, or a child of mDecor where the contents go.
private ViewGroup mContentParent;
......
private TextView mTitleView;
......
private CharSequence mTitle = null;
......
private void installDecor() {
if (mDecor == null) {
mDecor = generateDecor();
......
}
if (mContentParent == null) {
mContentParent = generateLayout(mDecor);
mTitleView = (TextView)findViewById(com.android.internal.R.id.title);
if (mTitleView != null) {
if ((getLocalFeatures() & (1 << FEATURE_NO_TITLE)) != 0) {
View titleContainer = findViewById(com.android.internal.R.id.title_container);
if (titleContainer != null) {
titleContainer.setVisibility(View.GONE);
} else {
mTitleView.setVisibility(View.GONE);
}
if (mContentParent instanceof FrameLayout) {
((FrameLayout)mContentParent).setForeground(null);
}
} else {
mTitleView.setText(mTitle);
}
}
}
}
......
} PhoneWindow的setContentView方法
@Override
public void setContentView(int layoutResID) {
if (mContentParent == null) {
installDecor();
} else {
mContentParent.removeAllViews();
}
mLayoutInflater.inflate(layoutResID, mContentParent);
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
} protected ViewGroup generateLayout(DecorView decor) {
// 获取mLayoutInflater.inflate(layoutResID, mContentParent);根据上面所有的猜测和分析，最终发现Window、DecorView和mContentParent的层级关系如下图（如有误请指正）
参考资料：
Window窗口布局--DecorView浅析
Android应用程序窗口（Activity）的视图对象（View）的创建过程分析