我们在Activity创建的时候，都用调用setContentView()函数来设置界面，下面我们通过源码来分析setContentView()的流程。
我们先看Activity里面的setContentView进去查看：
/**
* Set the activity content from a layout resource. The resource will be
* inflated, adding all top-level views to the activity.
*
* @param layoutResID Resource ID to be inflated.
*
* @see #setContentView(android.view.View)
* @see #setContentView(android.view.View, android.view.ViewGroup.LayoutParams)
*/
public void setContentView(@LayoutRes int layoutResID) {
getWindow().setContentView(layoutResID);
initWindowDecorActionBar();
}
函数如下:
我们再次点击setContentView进去查看发现是一个Window的抽象方法,所以我们要找到对应的实现类，我们点击getWindow()进去查看最终得到:
mWindow = new PhoneWindow(this, window);
我们得到了他的实现类PhoneWindow，然后在PhoneWindow找到setContentView函数:
@Override
public void setContentView(int layoutResID) {
// Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window
// decor, when theme attributes and the like are crystalized. Do not check the feature
// before this happens.
if (mContentParent == null) {
installDecor();
} else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
mContentParent.removeAllViews();
}
if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
getContext());
transitionTo(newScene);
} else {
mLayoutInflater.inflate(layoutResID, mContentParent);
}
mContentParent.requestApplyInsets();
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
}
@Override
public void setContentView(View view) {
setContentView(view, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
}
@Override
public void setContentView(View view, ViewGroup.LayoutParams params) {
// Note: FEATURE_CONTENT_TRANSITIONS may be set in the process of installing the window
// decor, when theme attributes and the like are crystalized. Do not check the feature
// before this happens.
if (mContentParent == null) {
installDecor();
} else if (!hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
mContentParent.removeAllViews();
}
if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
view.setLayoutParams(params);
final Scene newScene = new Scene(mContentParent, view);
transitionTo(newScene);
} else {
mContentParent.addView(view, params);
}
mContentParent.requestApplyInsets();
final Callback cb = getCallback();
if (cb != null && !isDestroyed()) {
cb.onContentChanged();
}
}
可以发现都是把这个View加到了mContentParent这个ViewGroup里面去了，这个mContentParent是什么呢？我们急着看源码,发现在installDecor()方法里面:
mContentParent = generateLayout(mDecor);
继续点进去:
protected ViewGroup generateLayout(DecorView decor) {
// Apply data from current theme.
TypedArray a = getWindowStyle();
if (false) {
System.out.println("From style:");
String s = "Attrs:";
for (int i = 0; i < R.styleable.Window.length; i++) {
s = s + " " + Integer.toHexString(R.styleable.Window[i
]) + "="
+ a.getString(i);
}
System.out.println(s);
}
//根据style属性做一些列的判断...
//在做一些列的判断得到layoutResource
layoutResource=.... //这里用R.layout.screen_simple来分析
mDecor.startChanging();
View in = mLayoutInflater.inflate(layoutResource, null);
decor.addView(in, new ViewGroup.LayoutParams(MATCH_PARENT, MATCH_PARENT));
mContentRoot = (ViewGroup) in;
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
if (contentParent == null) {
throw new RuntimeException("Window couldn't find content container view");
}
//......
mDecor.finishChanging();
return contentParent;
}
从这段代码可以知道，通过一系列的判断，得到相对于的layoutResource,然后通过mLayoutInflater.inflate(layoutResource, null);得到这个View,将其加入到mDecor,其中mContentParent最终为一个ID_ANDROID_CONTENT = com.android.internal.R.id.content的一个ViewGroup，在这里我们拿R.layout.screen_simple布局来看看
<?xml version="1.0" encoding="utf-8"?>
<!--
/* //device/apps/common/assets/res/layout/screen_simple.xml
**
** Copyright 2006, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
** http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
This is an optimized layout for a screen, with the minimum set of features
enabled.
-->
<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"
android:theme="?attr/actionBarTheme" />
<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>
可以知道这个mContentParent为一个FrameLayout，这时候我们应该知道，我们setContentView其实就是把那个View加入到一个id为com.android.internal.R.id.content的FrameLayout里面，而这个id为com.android.internal.R.id.content的FrameLayout有parentView又是加在mDecor里面，我们来看看这个mDecor是什么，在installDecor()函数中:
if (mDecor == null) {
mDecor = generateDecor();
mDecor.setDescendantFocusability(ViewGroup.FOCUS_AFTER_DESCENDANTS);
mDecor.setIsRootNamespace(true);
if (!mInvalidatePanelMenuPosted && mInvalidatePanelMenuFeatures != 0) {
mDecor.postOnAnimation(mInvalidatePanelMenuRunnable);
}
}
protected DecorView generateDecor() {
return new DecorView(getContext(), -1);
}
可以发现这个mDecor就是一个new的一个DecorView,我们继续看：
private final class DecorView extends FrameLayout
这个DecorView其实也是一个FrameLayout,这个时候我们就可以得到这样一张图:
在这基础上我们看AppCompatActivity的setContentView函数:
@Override
public void setContentView(@LayoutRes int layoutResID) {
getDelegate().setContentView(layoutResID);
}
/**
* @return The {@link AppCompatDelegate} being used by this Activity.
*/
@NonNull
public AppCompatDelegate getDelegate() {
if (mDelegate == null) {
mDelegate = AppCompatDelegate.create(this, this);
}
return mDelegate;
}
/**
* Create a {@link android.support.v7.app.AppCompatDelegate} to use with {@code activity}.
*
* @param callback An optional callback for AppCompat specific events
*/
public static AppCompatDelegate create(Activity activity, AppCompatCallback callback) {
return create(activity, activity.getWindow(), callback);
}
private static AppCompatDelegate create(Context context, Window window,
AppCompatCallback callback) {
final int sdk = Build.VERSION.SDK_INT;
if (sdk >= 23) {
return new AppCompatDelegateImplV23(context, window, callback);
} else if (sdk >= 14) {
return new AppCompatDelegateImplV14(context, window, callback);
} else if (sdk >= 11) {
return new AppCompatDelegateImplV11(context, window, callback);
} else {
return new AppCompatDelegateImplV7(context, window, callback);
}
}
可以看到最终进入到了AppCompatDelegate的create方法,这个函数通过new 23 14 11 7就可以看出是为了兼容不同的版本,我们点进去就可以看到AppCompatDelegateImplV23-->AppCompatDelegateImplV14-->AppCompatDelegateImplV11-->AppCompatDelegateImplV7依次继承的，我们最终查看到AppCompatDelegateImplV7的setContentView函数:
@Override
public void setContentView(View v) {
ensureSubDecor();
ViewGroup contentParent = (ViewGroup) mSubDecor.findViewById(android.R.id.content);
contentParent.removeAllViews();
contentParent.addView(v);
mOriginalWindowCallback.onContentChanged();
}
@Override
public void setContentView(int resId) {
ensureSubDecor();
ViewGroup contentParent = (ViewGroup) mSubDecor.findViewById(android.R.id.content);
contentParent.removeAllViews();
LayoutInflater.from(mContext).inflate(resId, contentParent);
mOriginalWindowCallback.onContentChanged();
}
@Override
public void setContentView(View v, ViewGroup.LayoutParams lp) {
ensureSubDecor();
ViewGroup contentParent = (ViewGroup) mSubDecor.findViewById(android.R.id.content);
contentParent.removeAllViews();
contentParent.addView(v, lp);
mOriginalWindowCallback.onContentChanged();
}
其实也就是把得到的view添加到contentParent里面。
比如说，在android21以前一般是使用控件TextView等控件，在21以后出了相关的AppCompat控件，这个时候怎么让开发者写的TextView自动转换为AppCompatTextView呢？所以在AppCompatDelegateImplV7重写了这样一个函数函数:
@Override
public void installViewFactory() {
LayoutInflater layoutInflater = LayoutInflater.from(mContext);
if (layoutInflater.getFactory() == null) {
LayoutInflaterCompat.setFactory(layoutInflater, this);
} else {
if (!(LayoutInflaterCompat.getFactory(layoutInflater)
instanceof AppCompatDelegateImplV7)) {
Log.i(TAG, "The Activity's LayoutInflater already has a Factory installed"
+ " so we can not install AppCompat's");
}
}
}
我们查找abstract类，可以查看着方法注释:
/**
* Installs AppCompat's {@link android.view.LayoutInflater} Factory so that it can replace
* the framework widgets with compatible tinted versions. This should be called before
* {@code super.onCreate()} as so:
* <pre class="prettyprint">
* protected void onCreate(Bundle savedInstanceState) {
* getDelegate().installViewFactory();
* getDelegate().onCreate(savedInstanceState);
* super.onCreate(savedInstanceState);
*
* // ...
* }
* </pre>
* If you are using your own {@link android.view.LayoutInflater.Factory Factory} or
* {@link android.view.LayoutInflater.Factory2 Factory2} then you can omit this call, and instead call
* {@link #createView(android.view.View, String, android.content.Context, android.util.AttributeSet)}
* from your factory to return any compatible widgets.
*/
public abstract void installViewFactory();
从意思可以看出，就是说我们可以通过这个方法然后给LayoutInflater设置一个Factory,这个Factory是干嘛的呢？从我的上篇文章就知道，这个Factory是在LayoutInflater执行inflate函数生成View的时候用的，这个Factory可以拦截View的生成，通过这个Factory我们可以自己给inflate写一套解析layout.xml的规则，在换肤的时候就可以用到这个。我们实现LayoutInflaterFactory接口，重写onCreateView方法，就可以拦截相应的信息进行解析。比如在AppCompatDelegateImplV7类中:
/**
* From {@link android.support.v4.view.LayoutInflaterFactory}
*/
@Override
public final View onCreateView(View parent, String name,
Context context, AttributeSet attrs) {
// First let the Activity's Factory try and inflate the view
final View view = callActivityOnCreateView(parent, name, context, attrs);
if (view != null) {
return view;
}
// If the Factory didn't handle it, let our createView() method try
return createView(parent, name, context, attrs);
}
View callActivityOnCreateView(View parent, String name, Context context, AttributeSet attrs) {
// Let the Activity's LayoutInflater.Factory try and handle it
if (mOriginalWindowCallback instanceof LayoutInflater.Factory) {
final View result = ((LayoutInflater.Factory) mOriginalWindowCallback)
.onCreateView(name, context, attrs);
if (result != null) {
return result;
}
}
return null;
}
@Override
public View createView(View parent, final String name, @NonNull Context context,
@NonNull AttributeSet attrs) {
final boolean isPre21 = Build.VERSION.SDK_INT < 21;
if (mAppCompatViewInflater == null) {
mAppCompatViewInflater = new AppCompatViewInflater();
}
// We only want the View to inherit its context if we're running pre-v21
final boolean inheritContext = isPre21 && shouldInheritContext((ViewParent) parent);
return mAppCompatViewInflater.createView(parent, name, context, attrs, inheritContext,
isPre21, /* Only read android:theme pre-L (L+ handles this anyway) */
true /* Read read app:theme as a fallback at all times for legacy reasons */
);
}
它拦截下了layoutt.xml的解析，自己写了一个解析类AppCompatViewInflater，来解析View
/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.support.v7.app;
import android.content.Context;
import android.content.ContextWrapper;
import android.content.res.TypedArray;
import android.os.Build;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.util.ArrayMap;
import android.support.v4.view.ViewCompat;
import android.support.v7.appcompat.R;
import android.support.v7.view.ContextThemeWrapper;
import android.support.v7.widget.AppCompatAutoCompleteTextView;
import android.support.v7.widget.AppCompatButton;
import android.support.v7.widget.AppCompatCheckBox;
import android.support.v7.widget.AppCompatCheckedTextView;
import android.support.v7.widget.AppCompatEditText;
import android.support.v7.widget.AppCompatImageButton;
import android.support.v7.widget.AppCompatImageView;
import android.support.v7.widget.AppCompatMultiAutoCompleteTextView;
import android.support.v7.widget.AppCompatRadioButton;
import android.support.v7.widget.AppCompatRatingBar;
import android.support.v7.widget.AppCompatSeekBar;
import android.support.v7.widget.AppCompatSpinner;
import android.support.v7.widget.AppCompatTextView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.InflateException;
import android.view.View;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Map;
/**
* This class is responsible for manually inflating our tinted widgets which are used on devices
* running {@link android.os.Build.VERSION_CODES#KITKAT KITKAT} or below. As such, this class
* should only be used when running on those devices.
* <p>This class two main responsibilities: the first is to 'inject' our tinted views in place of
* the framework versions in layout inflation; the second is backport the {@code android:theme}
* functionality for any inflated widgets. This include theme inheritance from it's parent.
*/
class AppCompatViewInflater {
private static final Class<?>[] sConstructorSignature = new Class[]{
Context.class, AttributeSet.class};
private static final int[] sOnClickAttrs = new int[]{android.R.attr.onClick};
private static final String[] sClassPrefixList = {
"android.widget.",
"android.view.",
"android.webkit."
};
private static final String LOG_TAG = "AppCompatViewInflater";
private static final Map<String, Constructor<? extends View>> sConstructorMap
= new ArrayMap<>();
private final Object[] mConstructorArgs = new Object[2];
public final View createView(View parent, final String name, @NonNull Context context,
@NonNull AttributeSet attrs, boolean inheritContext,
boolean readAndroidTheme, boolean readAppTheme) {
final Context originalContext = context;
// We can emulate Lollipop's android:theme attribute propagating down the view hierarchy
// by using the parent's context
if (inheritContext && parent != null) {
context = parent.getContext();
}
if (readAndroidTheme || readAppTheme) {
// We then apply the theme on the context, if specified
context = themifyContext(context, attrs, readAndroidTheme, readAppTheme);
}
View view = null;
// We need to 'inject' our tint aware Views in place of the standard framework versions
switch (name) {
case "TextView":
view = new AppCompatTextView(context, attrs);
break;
case "ImageView":
view = new AppCompatImageView(context, attrs);
break;
case "Button":
view = new AppCompatButton(context, attrs);
break;
case "EditText":
view = new AppCompatEditText(context, attrs);
break;
case "Spinner":
view = new AppCompatSpinner(context, attrs);
break;
case "ImageButton":
view = new AppCompatImageButton(context, attrs);
break;
case "CheckBox":
view = new AppCompatCheckBox(context, attrs);
break;
case "RadioButton":
view = new AppCompatRadioButton(context, attrs);
break;
case "CheckedTextView":
view = new AppCompatCheckedTextView(context, attrs);
break;
case "AutoCompleteTextView":
view = new AppCompatAutoCompleteTextView(context, attrs);
break;
case "MultiAutoCompleteTextView":
view = new AppCompatMultiAutoCompleteTextView(context, attrs);
break;
case "RatingBar":
view = new AppCompatRatingBar(context, attrs);
break;
case "SeekBar":
view = new AppCompatSeekBar(context, attrs);
break;
}
if (view == null && originalContext != context) {
// If the original context does not equal our themed context, then we need to manually
// inflate it using the name so that android:theme takes effect.
view = createViewFromTag(context, name, attrs);
}
if (view != null) {
// If we have created a view, check it's android:onClick
checkOnClickListener(view, attrs);
}
return view;
}
private View createViewFromTag(Context context, String name, AttributeSet attrs) {
if (name.equals("view")) {
name = attrs.getAttributeValue(null, "class");
}
try {
mConstructorArgs[0] = context;
mConstructorArgs[1] = attrs;
if (-1 == name.indexOf('.')) {
for (int i = 0; i < sClassPrefixList.length; i++) {
final View view = createView(context, name, sClassPrefixList[i]);
if (view != null) {
return view;
}
}
return null;
} else {
return createView(context, name, null);
}
} catch (Exception e) {
// We do not want to catch these, lets return null and let the actual LayoutInflater
// try
return null;
} finally {
// Don't retain references on context.
mConstructorArgs[0] = null;
mConstructorArgs[1] = null;
}
}
/**
* android:onClick doesn't handle views with a ContextWrapper context. This method
* backports new framework functionality to traverse the Context wrappers to find a
* suitable target.
*/
private void checkOnClickListener(View view, AttributeSet attrs) {
final Context context = view.getContext();
if (!(context instanceof ContextWrapper) ||
(Build.VERSION.SDK_INT >= 15 && !ViewCompat.hasOnClickListeners(view))) {
// Skip our compat functionality if: the Context isn't a ContextWrapper, or
// the view doesn't have an OnClickListener (we can only rely on this on API 15+ so
// always use our compat code on older devices)
return;
}
final TypedArray a = context.obtainStyledAttributes(attrs, sOnClickAttrs);
final String handlerName = a.getString(0);
if (handlerName != null) {
view.setOnClickListener(new DeclaredOnClickListener(view, handlerName));
}
a.recycle();
}
private View createView(Context context, String name, String prefix)
throws ClassNotFoundException, InflateException {
Constructor<? extends View> constructor = sConstructorMap.get(name);
try {
if (constructor == null) {
// Class not found in the cache, see if it's real, and try to add it
Class<? extends View> clazz = context.getClassLoader().loadClass(
prefix != null ? (prefix + name) : name).asSubclass(View.class);
constructor = clazz.getConstructor(sConstructorSignature);
sConstructorMap.put(name, constructor);
}
constructor.setAccessible(true);
return constructor.newInstance(mConstructorArgs);
} catch (Exception e) {
// We do not want to catch these, lets return null and let the actual LayoutInflater
// try
return null;
}
}
/**
* Allows us to emulate the {@code android:theme} attribute for devices before L.
*/
private static Context themifyContext(Context context, AttributeSet attrs,
boolean useAndroidTheme, boolean useAppTheme) {
final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.View, 0, 0);
int themeId = 0;
if (useAndroidTheme) {
// First try reading android:theme if enabled
themeId = a.getResourceId(R.styleable.View_android_theme, 0);
}
if (useAppTheme && themeId == 0) {
// ...if that didn't work, try reading app:theme (for legacy reasons) if enabled
themeId = a.getResourceId(R.styleable.View_theme, 0);
if (themeId != 0) {
Log.i(LOG_TAG, "app:theme is now deprecated. "
+ "Please move to using android:theme instead.");
}
}
a.recycle();
if (themeId != 0 && (!(context instanceof ContextThemeWrapper)
|| ((ContextThemeWrapper) context).getThemeResId() != themeId)) {
// If the context isn't a ContextThemeWrapper, or it is but does not have
// the same theme as we need, wrap it in a new wrapper
context = new ContextThemeWrapper(context, themeId);
}
return context;
}
/**
* An implementation of OnClickListener that attempts to lazily load a
* named click handling method from a parent or ancestor context.
*/
private static class DeclaredOnClickListener implements View.OnClickListener {
private final View mHostView;
private final String mMethodName;
private Method mResolvedMethod;
private Context mResolvedContext;
public DeclaredOnClickListener(@NonNull View hostView, @NonNull String methodName) {
mHostView = hostView;
mMethodName = methodName;
}
@Override
public void onClick(@NonNull View v) {
if (mResolvedMethod == null) {
resolveMethod(mHostView.getContext(), mMethodName);
}
try {
mResolvedMethod.invoke(mResolvedContext, v);
} catch (IllegalAccessException e) {
throw new IllegalStateException(
"Could not execute non-public method for android:onClick", e);
} catch (InvocationTargetException e) {
throw new IllegalStateException(
"Could not execute method for android:onClick", e);
}
}
@NonNull
private void resolveMethod(@Nullable Context context, @NonNull String name) {
while (context != null) {
try {
if (!context.isRestricted()) {
final Method method = context.getClass().getMethod(mMethodName, View.class);
if (method != null) {
mResolvedMethod = method;
mResolvedContext = context;
return;
}
}
} catch (NoSuchMethodException e) {
// Failed to find method, keep searching up the hierarchy.
}
if (context instanceof ContextWrapper) {
context = ((ContextWrapper) context).getBaseContext();
} else {
// Can't search up the hierarchy, null out and fail.
context = null;
}
}
final int id = mHostView.getId();
final String idText = id == View.NO_ID ? "" : " with id '"
+ mHostView.getContext().getResources().getResourceEntryName(id) + "'";
throw new IllegalStateException("Could not find method " + mMethodName
+ "(View) in a parent or ancestor Context for android:onClick "
+ "attribute defined on view " + mHostView.getClass() + idText);
}
}
}
这样就达到了将以前的TextView等转换为相关的AppCompat控件，达到兼容。
setContentView()源码流程就分析到这里,细看请自行查看源码。
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