Android Window布局建立流程分析

时间  2020-05-09
标签 android window 布局 建立 流程 分析 栏目 Android 繁體版
原文   原文链接

前言java

       关于android绘制流程的分析林林总总，虽然看过不少博客，但记住的东西却屈指可数。阅读别人写的文章远没有本身去捋一遍思路来的记忆深入。写文章的过程是帮助本身思考的过程，在思考的过程当中就会造成沉淀，从而达到技能的提高。android

一.见见森林

      学习应该是从总体到局部的，一头扎到代码中去每每会只见树木不见森林，因此我们今天就来先见见深林，噢 我不是说半z深林，首先看一下window总体结构，以下图所示：windows

 

        布局最外层是decorview，decorview和window的关系是：window有一个decorview。PhoneWindow是window的惟一实现类。decorview中是一个LinearLayout，其中包括一个viewstub和framlayout；framelayout中添加了subdecor, subdecor是一个viewgroup；subdecor中添加了一个linerlayout，包括一个actionbarcontainer和一个framlayout即上图的content，在activity oncreate中设置的布局将添加到content中。bash

 二.见见树木

     对整体有过认识以后，就能够看一下具体的实现过程。咱们将从外到内逐层分析其实现程，  app

（1）首先是PhoneWindow的实例化过程

   在ActivityThread的performLaunchActivity调用activity的attach方法，在attach方法中建立了PhoneWindow，以下所示ide

private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
    ...
    Activity activity = null;
    java.lang.ClassLoader cl = appContext.getClassLoader();
    activity = mInstrumentation.newActivity(
            cl, component.getClassName(), r.intent);
    ...
   activity.attach(appContext, this, getInstrumentation(), r.token,
        r.ident, app, r.intent, r.activityInfo, title, r.parent,
        r.embeddedID, r.lastNonConfigurationInstances, config,
        r.referrer, r.voiceInteractor, window, r.configCallback); 
  ...              
}
//在Activity中 新建phonewindow 一个activity对应一个phonewindow
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, String referrer, IVoiceInteractor voiceInteractor,
        Window window, ActivityConfigCallback activityConfigCallback) {
            ...
            mWindow = new PhoneWindow(this, window, activityConfigCallback);
            mWindow.setWindowControllerCallback(this);
            mWindow.setCallback(this);
            mWindow.setOnWindowDismissedCallback(this);
            mWindow.getLayoutInflater().setPrivateFactory(this);
            ...
        }复制代码

（2） 实例化DecorView 并使PhoneWindow中的mDecor引用指向实例化的DecorView

         decorview的添加发生在 activity oncreate中调用setContentView()的时候，最终走到  AppCompatDelegateImpl的方法中以下： 

public void setContentView(int resId){
    //添加subdecor
    ensureSubDecor();
    ViewGroup contentParent = (ViewGroup) mSubDecor.findViewById(android.R.id.content);
    contentParent.removeAllViews();
     //添加本身写的布局
    LayoutInflater.from(mContext).inflate(resId, contentParent);//在subdecor的content添加咱们的布局
    mOriginalWindowCallback.onContentChanged();
}复制代码

在 ensureSubDecor()方法中， 

private void ensureSubDecor() {
    if (!mSubDecorInstalled) {
       //若是未添加过subdecor则实例化一个
        mSubDecor = createSubDecor();
        ...
    }
}

private ViewGroup createSubDecor() {
    TypedArray a = mContext.obtainStyledAttributes(R.styleable.AppCompatTheme);
    ...

    // Now let's make sure that the Window has installed its decor by retrieving it mWindow.getDecorView(); final LayoutInflater inflater = LayoutInflater.from(mContext); ViewGroup subDecor = null; //更具设置的不一样feature，inflate subdecor if (!mWindowNoTitle) { if (mIsFloating) { // If we're floating, inflate the dialog title decor
            subDecor = (ViewGroup) inflater.inflate(
                    R.layout.abc_dialog_title_material, null);

            // Floating windows can never have an action bar, reset the flags
            mHasActionBar = mOverlayActionBar = false;
        } else if  
         .....
        } else {
            subDecor = (ViewGroup) inflater.inflate(R.layout.abc_screen_simple, null);
        }
    }

    final ContentFrameLayout contentView = (ContentFrameLayout) subDecor.findViewById(
            R.id.action_bar_activity_content);//subdecor的content

    final ViewGroup windowContentView = (ViewGroup) mWindow.findViewById(android.R.id.content);
    if (windowContentView != null) {
        // There might be Views already added to the Window's content view so we need to // migrate them to our content view while (windowContentView.getChildCount() > 0) { final View child = windowContentView.getChildAt(0); windowContentView.removeViewAt(0); contentView.addView(child); } // Change our content FrameLayout to use the android.R.id.content id. // Useful for fragments. windowContentView.setId(View.NO_ID); contentView.setId(android.R.id.content); } // Now set the Window's content view with the decor
    mWindow.setContentView(subDecor);
    return subDecor;
}
复制代码

具体看一下啊 mWindow.getDecorView()方法,简单的调用了installDecor(),若是decorView为null则建立一个，添加布局并将布局中的framelayout设置给 mContentParent ，在添加subdecor的时候将用到，至此decorview添加完成。 

public class PhoneWindow extends Window -> public final View getDecorView() {
    if (mDecor == null || mForceDecorInstall) {
        installDecor();
    }
    return mDecor;
}

private void installDecor() {
    mForceDecorInstall = false;
    if (mDecor == null) {
        mDecor = generateDecor(-1);
    } else {
        mDecor.setWindow(this);
    }
    if (mContentParent == null) {
        mContentParent = generateLayout(mDecor);

        // Set up decor part of UI to ignore fitsSystemWindows if appropriate.
        mDecor.makeOptionalFitsSystemWindows();

        final DecorContentParent decorContentParent = (DecorContentParent) mDecor.findViewById(
                R.id.decor_content_parent);
   }
}

protected DecorView generateDecor(int featureId) {
    ....
    return new DecorView(context, featureId, this, getAttributes()); //public class DecorView extends FrameLayout
}

protected ViewGroup generateLayout(DecorView decor) {
    // Apply data from current theme.
      ....
    WindowManager.LayoutParams params = getAttributes();
    
    // Inflate the window decor.
    int layoutResource;
    int features = getLocalFeatures();
    // System.out.println("Features: 0x" + Integer.toHexString(features));
    if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {
        ....
        // Embedded, so no decoration is needed.
        layoutResource = R.layout.screen_simple;
        // System.out.println("Simple!");
    }

    mDecor.startChanging();
    mDecor.onResourcesLoaded(mLayoutInflater, layoutResource);
 //decorview布局中的framelayout 即为subdecor的容器
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
if (contentParent == null) {
throw new RuntimeException("Window couldn't find content container view"); }
mDecor.finishChanging();
return contentParent;
}复制代码

（3） subdecor的添加过程

    在第二部的createSubDecor() 方法中，添加了subdecor，具体以下布局

private ViewGroup createSubDecor() {
    TypedArray a = mContext.obtainStyledAttributes(R.styleable.AppCompatTheme);
    ...
    // Now let's make sure that the Window has installed its decor by retrieving it mWindow.getDecorView(); final LayoutInflater inflater = LayoutInflater.from(mContext); ViewGroup subDecor = null; 1.//更具设置的不一样feature，inflate subdecor if (!mWindowNoTitle) { if (mIsFloating) { // If we're floating, inflate the dialog title decor
            subDecor = (ViewGroup) inflater.inflate(
                    R.layout.abc_dialog_title_material, null);

            // Floating windows can never have an action bar, reset the flags
            mHasActionBar = mOverlayActionBar = false;
        } else if  
         .....
        } else {
            subDecor = (ViewGroup) inflater.inflate(R.layout.abc_screen_simple, null);
        }
    }
 2.//subdecor的content
final ContentFrameLayout contentView = (ContentFrameLayout) subDecor.findViewById(            R.id.action_bar_activity_content);

    final ViewGroup windowContentView = (ViewGroup) mWindow.findViewById(android.R.id.content);
    if (windowContentView != null) {
        // There might be Views already added to the Window's content view so we need to // migrate them to our content view while (windowContentView.getChildCount() > 0) { final View child = windowContentView.getChildAt(0); windowContentView.removeViewAt(0); contentView.addView(child); } // Change our content FrameLayout to use the android.R.id.content id. // Useful for fragments. windowContentView.setId(View.NO_ID); //将subdecor中的framelayout id设置为content contentView.setId(android.R.id.content); } 3.// Now set the Window's content view with the decor
    mWindow.setContentView(subDecor);
    return subDecor;
}复制代码

  具体看一下  mWindow.setContentView(subDecor)方法，实如今phonewindow中，在mContentParent 中添加subdecor，mContentParent为decorview中的framelayout至此subdecor添加完成 

@Override
    public void setContentView(View view, ViewGroup.LayoutParams params) {
     
        if (mContentParent == null) {
            installDecor();
        } else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
            mContentParent.removeAllViews();
        }
        mContentParent.addView(view, params);
    }复制代码

 (4)  activity oncreate 中setContentView布局的添加，见第二步中的方法

public void setContentView(int resId){
    //添加subdecor
    ensureSubDecor();
   //找到content容器
    ViewGroup contentParent = (ViewGroup) mSubDecor.findViewById(android.R.id.content);
    contentParent.removeAllViews();
     //添加本身写的布局
    LayoutInflater.from(mContext).inflate(resId, contentParent);//在subdecor的content添加咱们的布局
    mOriginalWindowCallback.onContentChanged();
}复制代码

至此，整个window 布局添加完成，以后即是将布局绘制到屏幕上。学习

相关文章
相关标签/搜索
每日一句
    每一个你不满意的现在，都有一个你没有努力的曾经。
本站公众号
   欢迎关注本站公众号,获取更多信息
联系我们 最近搜索 最新文章 沪ICP备13005482号-10 MyBatis教程 SQL 教程 MySQL教程 Java 教程 Thymeleaf 教程 Hibernate教程 Spring教程 Redis教程