首先看activity的setContentView的源码
public void setContentView(@LayoutRes int layoutResID) {
getWindow().setContentView(layoutResID);
initWindowDecorActionBar();
}
我们点击setContetnView会发现此是个抽象方法，这时候我们看下getWindow的方法我们最终会发现它实际是PhoneWindow
mWindow = new PhoneWindow(this, window, activityConfigCallback);
我们看PhoneWindow的setContentView的源码
@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();
}
if (hasFeature(FEATURE_CONTENT_TRANSITIONS)) {
final Scene newScene = Scene.getSceneForLayout(mContentParent, layoutResID,
getContext());
transitionTo(newScene);
} else {
//最后我们将我们设置的布局设置mContentParent进去
mLayoutInflater.inflate(layoutResID, mContentParent);
}
}
installDecor源码分析
if (mDecor == null) {
mDecor = generateDecor(-1);
} else {
mDecor.setWindow(this);
}
if (mContentParent == null) {
mContentParent = generateLayout(mDecor);
}
我们进去后我们会发现实际mDecor是继承于FrameLayout,重点我们看这个 mContentParent = generateLayout(mDecor);
protected ViewGroup generateLayout(DecorView decor) {
int layoutResource;
if ((features & (1 << FEATURE_SWIPE_TO_DISMISS)) != 0) {
layoutResource = R.layout.screen_swipe_dismiss;
setCloseOnSwipeEnabled(true);
} else {
layoutResource = R.layout.screen_simple;
// System.out.println("Simple!");
}
ViewGroup contentParent = (ViewGroup)findViewById(ID_ANDROID_CONTENT);
return contentParent;
}
因为源码太长就不全部粘贴了，直接贴重要的，我们看 R.layout.screen_simple;布局
<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>
好了这里我们可以看到了mContentParent = generateLayout(mDecor);实际返回的是系统里面的FrameLayout，最后我们发现setContentView调用的是 - mLayoutInflater.inflate(layoutResID, mContentParent);将自己的布局设置进去
activity源码阅读.png
AppCompatActivity的setContentView源码分析
@Override
public void setContentView(@LayoutRes int layoutResID) {
getDelegate().setContentView(layoutResID);
}
最终我的源码是调用的是AppCompatDelegateImplV9中的setContentView，用的源码可能是AppCompatDelegateImplV7
@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();
}
我们发现实际和Activity类似
我们来做个小实验，假设我们有个ImageView,当MainActivity继承于Activity的时候，我们打印imageview的时候，我们会发现是imageview,接下来我们将MainActivity继承于AppCompatActivity，我们会发现ImageView被换成了 android.support.v7.widget.AppCompatImageView,这时候我们会很好奇，怎么被换了，其实是被拦截了，我们来看下AppCompatActivity拦截的源码
回到AppCompatDelegateImplV9我们会发现 LayoutInflater.Factory2
class AppCompatDelegateImplV9 extends AppCompatDelegateImplBase
implements MenuBuilder.Callback, LayoutInflater.Factory2
LayoutInflater.Factory2这个方法就是拦截的重要方法我们可以看下它是怎么设置的,直接搜setFactory2
@Override
public void installViewFactory() {
LayoutInflater layoutInflater = LayoutInflater.from(mContext);
if (layoutInflater.getFactory() == null) {
LayoutInflaterCompat.setFactory2(layoutInflater, this);
} else {
if (!(layoutInflater.getFactory2() instanceof AppCompatDelegateImplV9)) {
Log.i(TAG, "The Activity's LayoutInflater already has a Factory installed"
+ " so we can not install AppCompat's");
}
}
}
我们点击setFactor2进去后我们会发现这个方法会重新复写onCreateView
@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);
}
一直走下去我们最终会发现源码
源码.png
看到这里我们知道它实际是被拦截了，这时候我们看下AppCompat在设置布局的时候是怎么拦截的
我们设置布局有很多方式 LayoutInflater.from(this).inflate()或者setContentView最终调用的都是这个方法
public View inflate(@LayoutRes int resource, @Nullable ViewGroup root, boolean attachToRoot) {
final Resources res = getContext().getResources();
if (DEBUG) {
Log.d(TAG, "INFLATING from resource: \"" + res.getResourceName(resource) + "\" ("
+ Integer.toHexString(resource) + ")");
}
final XmlResourceParser parser = res.getLayout(resource);
try {
return inflate(parser, root, attachToRoot);
} finally {
parser.close();
}
}
接下来我们找到以下的方法
final View temp = createViewFromTag(root, name, inflaterContext, attrs);
最后走到这里
View createViewFromTag(View parent, String name, Context context, AttributeSet attrs,
boolean ignoreThemeAttr) {
try {
View view;
if (mFactory2 != null) {//如果设置拦截则会走向这里
view = mFactory2.onCreateView(parent, name, context, attrs);
} else if (mFactory != null) {
view = mFactory.onCreateView(name, context, attrs);
} else {
view = null;
}
if (view == null && mPrivateFactory != null) {
view = mPrivateFactory.onCreateView(parent, name, context, attrs);
}
if (view == null) {
final Object lastContext = mConstructorArgs[0];
mConstructorArgs[0] = context;
try {
//是不是自己定义的View
if (-1 == name.indexOf('.')) {
view = onCreateView(parent, name, attrs);
} else {
view = createView(name, null, attrs);
}
} finally {
mConstructorArgs[0] = lastContext;
}
}
return view;
}
}
由上面我们可以做个小案例进行拦截View
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
LayoutInflater layoutInflater = LayoutInflater.from(this);
LayoutInflaterCompat.setFactory2(layoutInflater, new LayoutInflater.Factory2() {
@Override
public View onCreateView(View parent, String name, Context context, AttributeSet attrs) {
Log.e("TAG", "拦截view的创建");
if ("Button".equals(name)) {
TextView textView = new TextView(BaseSkinActivity.this);
textView.setText("拦截美女");
return textView;
}
return null;
}
@Override
public View onCreateView(String name, Context context, AttributeSet attrs) {
return null;
}
});
//一定要放在下面否则报错
super.onCreate(savedInstanceState);
//这方法已经过时了
/*LayoutInflaterCompat.setFactory(layoutInflater, new LayoutInflaterFactory() {
@Override
public View onCreateView(View parent, String name, Context context, AttributeSet attrs) {
return null;
}
});*/
}
