Android-自定义Factory2打造动态换肤（一）
目录
- 需求分析
- 流程
- 方案-自定义Factory2（通过阅读源码得知）
- 创建View的过程
- 代码-实战部分
需求分析
实现APP换肤的功能，要求：
- 为避免增加apk体积不预先内置资源包仅仅有一个默认的，因此需要实现动态换肤
- 换肤功能必须实时生效无需用户重启app
- 无闪烁换肤
- 字体、状态栏、自定义View、系统View 换肤
- Activity、Fragment换肤
流程
方案-自定义Factory2（通过阅读源码得知）
我们可以参考系统创建view的流程，在创建的过程中我们是否可以偷梁换柱呢？
首先我们通过setContentView(R.layout.activity_main)为入口进行追踪，看看系统到底是如何让View创建出来的。
通过getDelegate().setContentView(layoutResID);我们知道其实Activity很多操作都是由委托类AppCompatDelegate来实现的,通过源码我们还知道了AppCompatDelegate具体实现又是由子类AppCompatDelegateImpl来操作的。
我们接着看AppCompatDelegateImpl的setContentView(int resId)
@Override
public void setContentView(int resId) {
ensureSubDecor();
ViewGroup contentParent = mSubDecor.findViewById(android.R.id.content);
contentParent.removeAllViews();
//这个就是我们的目标
LayoutInflater.from(mContext).inflate(resId, contentParent);
mAppCompatWindowCallback.getWrapped().onContentChanged();
}
接着进入inflate(@LayoutRes int resource, @Nullable ViewGroup root)方法，接下来就是一路顺着inflater跟踪就可以了，下面就把无关紧要的跳转省略了
public View inflate(XmlPullParser parser, @Nullable ViewGroup root, boolean attachToRoot) {
//开始解析XML
synchronized (mConstructorArgs) {
...
...
try {
advanceToRootNode(parser);
//View的名字，ImageView/TextView
final String name = parser.getName();
if (DEBUG) {
System.out.println("**************************");
System.out.println("Creating root view: "
+ name);
System.out.println("**************************");
}
//merge view
if (TAG_MERGE.equals(name)) {
if (root == null || !attachToRoot) {
throw new InflateException("接着进入createViewFromTag
View createViewFromTag(View parent, String name, Context context, AttributeSet attrs,
boolean ignoreThemeAttr) {
...
...
try {
//创建view
View view = tryCreateView(parent, name, context, attrs);
//如果通过tryCreateView创建view依然为空，就使用默认的创建view的方式创建，也就是
//通过AppCompatDelegateImpl来创建view
if (view == null) {
final Object lastContext = mConstructorArgs[0];
mConstructorArgs[0] = context;
try {
//表示是系统View,比如TextView/ImageView等
if (-1 == name.indexOf('.')) {
view = onCreateView(context, parent, name, attrs);
} else {
view = createView(context, name, null, attrs);
}
} finally {
mConstructorArgs[0] = lastContext;
}
}
return view;
} catch (InflateException e) {
throw e;
} catch (ClassNotFoundException e) {
final InflateException ie = new InflateException(
getParserStateDescription(context, attrs)
+ ": Error inflating class " + name, e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} catch (Exception e) {
final InflateException ie = new InflateException(
getParserStateDescription(context, attrs)
+ ": Error inflating class " + name, e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
}
}
接着进入tryCreateView方法
public final View tryCreateView(@Nullable View parent, @NonNull String name,
@NonNull Context context,
@NonNull AttributeSet attrs) {
if (name.equals(TAG_1995)) {
// Let's party like it's 1995!
return new BlinkLayout(context, attrs);
}
View view;
//如果Factory2工厂不为空的话就是用Factory2来创建View
//通过源码我们知道系统并没有实现Factory2的onCreateView方法，咱们实现呗，这样咱们就可以对View
//进行为所欲为了
if (mFactory2 != null) {
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);
}
return view;
}
创建View的过程
既然我们要继承Factory2自然要实现其onCreateView的方法了，所以我们需要知道View到底是如何创建的，那么让我们看看源码吧,位置在AppCompatDelegateImpl
@Override
public View createView(View parent, final String name, @NonNull Context context,
@NonNull AttributeSet attrs) {
if (mAppCompatViewInflater == null) {
TypedArray a = mContext.obtainStyledAttributes(R.styleable.AppCompatTheme);
String viewInflaterClassName =
a.getString(R.styleable.AppCompatTheme_viewInflaterClass);
if ((viewInflaterClassName == null)
|| AppCompatViewInflater.class.getName().equals(viewInflaterClassName)) {
// Either default class name or set explicitly to null. In both cases
// create the base inflater (no reflection)
mAppCompatViewInflater = new AppCompatViewInflater();
} else {
try {
Class<?> viewInflaterClass = Class.forName(viewInflaterClassName);
mAppCompatViewInflater =
(AppCompatViewInflater) viewInflaterClass.getDeclaredConstructor()
.newInstance();
} catch (Throwable t) {
Log.i(TAG, "Failed to instantiate custom view inflater "
+ viewInflaterClassName + ". Falling back to default.", t);
mAppCompatViewInflater = new AppCompatViewInflater();
}
}
}
boolean inheritContext = false;
if (IS_PRE_LOLLIPOP) {
inheritContext = (attrs instanceof XmlPullParser)
// If we have a XmlPullParser, we can detect where we are in the layout
? ((XmlPullParser) attrs).getDepth() > 1
// Otherwise we have to use the old heuristic
: shouldInheritContext((ViewParent) parent);
}
return mAppCompatViewInflater.createView(parent, name, context, attrs, inheritContext,
IS_PRE_LOLLIPOP, /* Only read android:theme pre-L (L+ handles this anyway) */
true, /* Read read app:theme as a fallback at all times for legacy reasons */
VectorEnabledTintResources.shouldBeUsed() /* Only tint wrap the context if enabled */
);
}
通过源码我们发现真正创建View的是AppCompatViewInflater ，
final View createView(View parent, final String name, @NonNull Context context,
@NonNull AttributeSet attrs, boolean inheritContext,
boolean readAndroidTheme, boolean readAppTheme, boolean wrapContext) {
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);
}
if (wrapContext) {
context = TintContextWrapper.wrap(context);
}
View view = null;
// We need to 'inject' our tint aware Views in place of the standard framework versions
switch (name) {
case "TextView":
view = createTextView(context, attrs);
verifyNotNull(view, name);
break;
case "ImageView":
view = createImageView(context, attrs);
verifyNotNull(view, name);
break;
case "Button":
view = createButton(context, attrs);
verifyNotNull(view, name);
break;
case "EditText":
view = createEditText(context, attrs);
verifyNotNull(view, name);
break;
case "Spinner":
view = createSpinner(context, attrs);
verifyNotNull(view, name);
break;
case "ImageButton":
view = createImageButton(context, attrs);
verifyNotNull(view, name);
break;
case "CheckBox":
view = createCheckBox(context, attrs);
verifyNotNull(view, name);
break;
case "RadioButton":
view = createRadioButton(context, attrs);
verifyNotNull(view, name);
break;
case "CheckedTextView":
view = createCheckedTextView(context, attrs);
verifyNotNull(view, name);
break;
case "AutoCompleteTextView":
view = createAutoCompleteTextView(context, attrs);
verifyNotNull(view, name);
break;
case "MultiAutoCompleteTextView":
view = createMultiAutoCompleteTextView(context, attrs);
verifyNotNull(view, name);
break;
case "RatingBar":
view = createRatingBar(context, attrs);
verifyNotNull(view, name);
break;
case "SeekBar":
view = createSeekBar(context, attrs);
verifyNotNull(view, name);
break;
case "ToggleButton":
view = createToggleButton(context, attrs);
verifyNotNull(view, name);
break;
default:
// The fallback that allows extending class to take over view inflation
// for other tags. Note that we don't check that the result is not-null.
// That allows the custom inflater path to fall back on the default one
// later in this method.
view = createView(context, name, attrs);
}
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 its 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 = createViewByPrefix(context, name, sClassPrefixList[i]);
if (view != null) {
return view;
}
}
return null;
} else {
return createViewByPrefix(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;
}
}
private View createViewByPrefix(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 = Class.forName(
prefix != null ? (prefix + name) : name,
false,
context.getClassLoader()).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;
}
}
基本上上面这些我们可以复制过去直接拿去用就可以了，这里还有一个彩蛋就是TextView,ImageView,Button 等这些常用控件会被重新创建成AppCompatXXX,其实他就是一个低版本的兼容包，这样就能够在低版本上也能够最大化的实现5.0以上的效果了。
代码-实战部分
由于篇幅有限，本章就只分析如何实现吧，具体代码实现会放到下一章进行详细分享。也可以到GitHub看下具体的Code。
今天的分享就到这里，拜了个拜。