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);
}
在上篇博客onAttachedToWindow()在整个Activity生命周期的位置及使用中解释了为什么在onAttachedToWindow中修改窗口尺寸，上面代码最后两行分别对window和decorView设置背景，那么问题来了，一个窗体中decorView和window之间的关系是什么？
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);
}
......
}
Window原来是Activity的一个变量，可以通过getWindow()获取，而且Activity中经常用到的setContentView原来调用的是window的setContentView。那么Window是什么？在Activity中起什么作用？OK~带着问题再查阅Google的官方文档。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);
}
}
}
}
......
}
在这里总算找到了DecorView，和上面猜测的一样，DecorView确实为Window的变量。同时还发现一个名为mContentParent的ViewGroup，那么这个变量的作用是什么？和DecorView有什么关系？带着问题接着往下看。
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();
}
}
在mContentParent为null时会调用installDecor()来创建应用程序窗口视图对象。接着在installDecor()中调用generateLayout为mContentParent赋值。 protected ViewGroup generateLayout(DecorView decor) {
// 获取<Activity android:theme=""/>中的theme属性或者代码requestWindowFeature()中指定的Features
TypedArray a = getWindowStyle();
if (false) {
System.out.println("From style:");
String s = "Attrs:";
for (int i = 0; i < com.android.internal.R.styleable.Window.length; i++) {
s = s + " " + Integer.toHexString(com.android.internal.R.styleable.Window[i]) + "="
+ a.getString(i);
}
System.out.println(s);
}
mIsFloating = a.getBoolean(com.android.internal.R.styleable.Window_windowIsFloating, false);
int flagsToUpdate = (FLAG_LAYOUT_IN_SCREEN|FLAG_LAYOUT_INSET_DECOR)
& (~getForcedWindowFlags());
if (mIsFloating) {
setLayout(WRAP_CONTENT, WRAP_CONTENT);
setFlags(0, flagsToUpdate);
} else {
setFlags(FLAG_LAYOUT_IN_SCREEN|FLAG_LAYOUT_INSET_DECOR, flagsToUpdate);
}
//...
// Inflate the window decor.
int layoutResource;
int features = getLocalFeatures();
// System.out.println("Features: 0x" + Integer.toHexString(features));
if ((features & ((1 << FEATURE_LEFT_ICON) | (1 << FEATURE_RIGHT_ICON))) != 0) {
if (mIsFloating) {
TypedValue res = new TypedValue();
getContext().getTheme().resolveAttribute(
com.android.internal.R.attr.dialogTitleIconsDecorLayout, res, true);
layoutResource = res.resourceId;
} else {
layoutResource = com.android.internal.R.layout.screen_title_icons;
}
// XXX Remove this once action bar supports these features.
removeFeature(FEATURE_ACTION_BAR);
// System.out.println("Title Icons!");
} else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0
&& (features & (1 << FEATURE_ACTION_BAR)) == 0) {
// Special case for a window with only a progress bar (and title).
// XXX Need to have a no-title version of embedded windows.
layoutResource = com.android.internal.R.layout.screen_progress;
// System.out.println("Progress!");
} else if ((features & (1 << FEATURE_CUSTOM_TITLE)) != 0) {
// Special case for a window with a custom title.
// If the window is floating, we need a dialog layout
if (mIsFloating) {
TypedValue res = new TypedValue();
getContext().getTheme().resolveAttribute(
com.android.internal.R.attr.dialogCustomTitleDecorLayout, res, true);
layoutResource = res.resourceId;
} else {
layoutResource = com.android.internal.R.layout.screen_custom_title;
}
// XXX Remove this once action bar supports these features.
removeFeature(FEATURE_ACTION_BAR);
} else if ((features & (1 << FEATURE_NO_TITLE)) == 0) {
// If no other features and not embedded, only need a title.
// If the window is floating, we need a dialog layout
if (mIsFloating) {
TypedValue res = new TypedValue();
getContext().getTheme().resolveAttribute(
com.android.internal.R.attr.dialogTitleDecorLayout, res, true);
layoutResource = res.resourceId;
} else if ((features & (1 << FEATURE_ACTION_BAR)) != 0) {
layoutResource = com.android.internal.R.layout.screen_action_bar;
} else {
layoutResource = com.android.internal.R.layout.screen_title;
}
// System.out.println("Title!");
} else if ((features & (1 << FEATURE_ACTION_MODE_OVERLAY)) != 0) {
layoutResource = com.android.internal.R.layout.screen_simple_overlay_action_mode;
} else {
// Embedded, so no decoration is needed.
layoutResource = com.android.internal.R.layout.screen_simple;
// System.out.println("Simple!");
}
mDecor.startChanging();
View in = mLayoutInflater.inflate(layoutResource, null);
decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
if (contentParent == null) {
throw new RuntimeException("Window couldn't find content container view");
}
if ((features & (1 << FEATURE_INDETERMINATE_PROGRESS)) != 0) {
ProgressBar progress = getCircularProgressBar(false);
if (progress != null) {
progress.setIndeterminate(true);
}
}
// Remaining setup -- of background and title -- that only applies
// to top-level windows.
if (getContainer() == null) {
Drawable drawable = mBackgroundDrawable;
if (mBackgroundResource != 0) {
drawable = getContext().getResources().getDrawable(mBackgroundResource);
}
mDecor.setWindowBackground(drawable);
drawable = null;
if (mFrameResource != 0) {
drawable = getContext().getResources().getDrawable(mFrameResource);
}
mDecor.setWindowFrame(drawable);
// System.out.println("Text=" + Integer.toHexString(mTextColor) +
// " Sel=" + Integer.toHexString(mTextSelectedColor) +
// " Title=" + Integer.toHexString(mTitleColor));
if (mTitleColor == 0) {
mTitleColor = mTextColor;
}
if (mTitle != null) {
setTitle(mTitle);
}
setTitleColor(mTitleColor);
}
mDecor.finishChanging();
return contentParent;
}
上面代码可看到将一些页面特性布局，例如ActionBar、Title等添加到decorView中，并且根据代码ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);可看到原来mContentParent是id="@android:id/content"的ViewGroup。再回到PhoneWindow.setContentView
mLayoutInflater.inflate(layoutResID, mContentParent);原来我们自定义的View都是mContentParent的子View。并且上面这段代码还发现了为什么必须在setContentView之前才能执行requestWindowFeature的彩蛋。
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