首页 > 代码库 > Window窗口布局 --- DecorView浅析
Window窗口布局 --- DecorView浅析
开发中,通常都是在onCreate()中调用setContentView(R.layout.custom_layout)来实现想要的页面布局,我们知道,页面都是依附在窗口之上的,而DecorView即是窗口最顶层的视图。Android frameworks中,与窗口视图处理相关的类,主要是Window及其实现类PhoneWindow
public class PhoneWindow extends Window implements MenuBuilder.Callback {
//...
//窗口顶层View private DecorView mDecor;
//所有自定义View的根View, id="@android:id/content" private ViewGroup mContentParent;
DecorView其实是PhoneWindow中的一个内部类,本质上也是一个View,其只是扩展了FrameLayout的实现
private final class DecorView extends FrameLayout implements RootViewSurfaceTaker { //...
页面layout被添加至窗口Window的流程大致如下:
1,Activity中调用setContentView(R.layout.custom_layout), 具体实现为PhoneWindow中的同名方法
public void setContentView(int layoutResID) {
//getWindow()获取的即是PhoneWindow对象
getWindow().setContentView(layoutResID); }
2, PhoneWindow执行setContentView(int layoutResource)
public void setContentView(int layoutResID) {
//初始,mContentParent为空 if (mContentParent == null) { installDecor(); } else { mContentParent.removeAllViews(); }
//inflate自定义layout, 并将mContentParent作为其根视图 mLayoutInflater.inflate(layoutResID, mContentParent);
3, PhoneWindow.installDecor()
private void installDecor() { if (mDecor == null) {
//new一个DecorView mDecor = generateDecor(); mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS); mDecor.setIsRootNamespace(true); if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) { mDecor.postOnAnimation(mInvalidatePanelMenuRunnable); } } if (mContentParent == null) {
//这一步会设置窗口的修饰文件,并将id为ID_ANDROID_CONTENT的view find出来作为返回值赋值给mContentParent mContentParent = generateLayout(mDecor);
4, PhoneWindow.generateLayout(DecorView decor)
protected ViewGroup generateLayout(DecorView decor) { //4.1,获取<Application android:theme=""/>, <Activity/>节点指定的themes或者代码requestWindowFeature()中指定的Features, 并设置 TypedArray a = getWindowStyle(); //... //4.2,获取窗口Features, 设置相应的修饰布局文件,这些xml文件位于frameworks/base/core/res/res/layout下 int layoutResource; int features = getLocalFeatures(); 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; } removeFeature(FEATURE_ACTION_BAR); } else if ((features & ((1 << FEATURE_PROGRESS) | (1 << FEATURE_INDETERMINATE_PROGRESS))) != 0 && (features & (1 << FEATURE_ACTION_BAR)) == 0) { layoutResource = com.android.internal.R.layout.screen_progress; //...
mDecor.startChanging(); //4.3, 将上面选定的布局文件inflate为View树,添加到decorView中 View in = mLayoutInflater.inflate(layoutResource, null); decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT)); //将窗口修饰布局文件中id="@android:id/content"的View赋值给mContentParent, 后续自定义的view/layout都将是其子View ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT); if (contentParent == null) { throw new RuntimeException("Window couldn‘t find content container view"); }
//...
从上述步骤中,可以看出为什么在代码中必须要在setContentView(...)之前才能执行requestWindowFeature(...)
5, 最后页面中设置的自定义layout会被添加到mContentParent中
mLayoutInflater.inflate(layoutResID, mContentParent);
所以,Window窗口的布局层次结构(features不同,可能标题栏不存在, 这种情况下,窗口修饰视图区域与mContentParent内容区域重叠)如下所示:
示例:
Activity代码:
@Overrideprotected void onCreate(Bundle savedInstanceState) { //设置窗口无标题栏 requestWindowFeature(Window.FEATURE_NO_TITLE); super.onCreate(savedInstanceState); setContentView(R.layout.activity_decor);}
activity_decor.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".DecorActivity"> <TextView android:text="@string/hello_world" android:layout_width="wrap_content" android:layout_height="wrap_content" /> <TextView android:text="@string/hello_world" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentBottom="true"/></RelativeLayout>
onCreate()中设置的Window.FEATURE_NO_TITLE对应的窗口修饰布局文件为screen_simple.xml, 源码如下,
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:fitsSystemWindows="true" android:orientation="vertical"> <ViewStub android:id="@+id/action_mode_bar_stub" android:inflatedId="@+id/action_mode_bar" android:layout="@layout/action_mode_bar" android:layout_width="match_parent" android:layout_height="wrap_content" /> <FrameLayout android:id="@android:id/content" android:layout_width="match_parent" android:layout_height="match_parent" android:foregroundInsidePadding="false" android:foregroundGravity="fill_horizontal|top" android:foreground="?android:attr/windowContentOverlay" /></LinearLayout>
源码中id为"@android:id/content"的FrameLayout就是内容区域,在整个流程中,其会赋值给PhoneWindow类中的属性mContentParent, 运行应用后,使用SDK提供的hierarchyviewer工具查看页面的ViewTree结构,可以看到结构如下:
参考资料:
http://blog.csdn.net/qinjuning/article/details/7226787
http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/4.4.2_r1/android/view/Window.java?av=f
http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/4.4.2_r1/com/android/internal/policy/impl/PhoneWindow.java?av=f
http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/4.4.2_r1/frameworks/base/core/res/res/layout/screen_simple.xml?av=f
http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/4.4.2_r1/android/app/Activity.java?av=f
Window窗口布局 --- DecorView浅析