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完成换肤需要解决两个问题：
如何获取换肤的View，利用LayoutInflater内部接口Factory2提供的onCreateView方法获取需要换肤的View,我们从setContentView方法的具体作用来了解LayoutInflater.Factory2接口的作用，以具体源码进行分析，MainActivity代码如下：
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
复制代码MainActivity继承自AppCompatActivity，AppCompatActivity是Android Support Library包下的类，点击进入AppCompatActivity的setContentView方法：
@Override
public void setContentView(@LayoutRes int layoutResID) {
getDelegate().setContentView(layoutResID);
}
复制代码通过getDelegate()方法返回一个AppCompatDelegate对象，并调用AppCompatDelegate对象的setContentView方法。
@NonNull
public AppCompatDelegate getDelegate() {
if (mDelegate == null) {
mDelegate = AppCompatDelegate.create(this, this);
}
return mDelegate;
}
复制代码通过AppCompatDelegate的create方法创建AppCompatDelegate对象：
public static AppCompatDelegate create(Activity activity, AppCompatCallback callback) {
return create(activity, activity.getWindow(), callback);
}
复制代码通过create方法返回AppCompatDelegate对象：
private static AppCompatDelegate create(Context context, Window window,
AppCompatCallback callback) {
if (Build.VERSION.SDK_INT >= 24) {
return new AppCompatDelegateImplN(context, window, callback);
} else if (Build.VERSION.SDK_INT >= 23) {
return new AppCompatDelegateImplV23(context, window, callback);
} else {
return new AppCompatDelegateImplV14(context, window, callback);
}
}
复制代码AppCompatDelegate对象的创建是根据SDK的不同版本而创建的，其中AppCompatDelegateImplN、AppCompatDelegateImplV23以及AppCompatDelegateImplV14的继承结构如下图所示：
AppCompatDelegate是一个抽象类，AppCompatDelegateImplBase也是抽象类，主要对AppCompatDelegate功能的扩展，具体的实现类是AppCompatDelegateImplV9，以上根据SDK版本创建的类都继承自AppCompatDelegateImplV9。
继续回到AppCompatActivity的setContentView方法：
@Override
public void setContentView(@LayoutRes int layoutResID) {
getDelegate().setContentView(layoutResID);
}
复制代码获取AppCompatDelegate对象后，通过该对象的setContentView方法设置ContentView，这个setContentView方法的具体调用是在AppCompatDelegateImplV9中，查看源码如下：
//android.support.v7.app.AppCompatDelegateImplV9
@Override
public void setContentView(int resId) {
ensureSubDecor();
ViewGroup contentParent = (ViewGroup) mSubDecor.findViewById(android.R.id.content);
contentParent.removeAllViews();
//注释1
LayoutInflater.from(mContext).inflate(resId, contentParent);
mOriginalWindowCallback.onContentChanged();
}
复制代码setContentView方法最核心的地方就是在注释1处，通过LayoutInflater加载layout.xml文件，contentParent是我们创建布局后所要添加进去的一个容器，在创建Activity时会创建顶层视图，也就是DecorView，DecorView其实是PhoneWindow中的一个内部类，它会加载相应的系统布局。如下图：
DecorView就是我们Activity显示的全部视图包括ActionBar，其中ContentView布局是由我们来创建的，并通过LayoutInflater添加到ContentView中。
进入LayoutInflater的inflate方法中。
public View inflate(@LayoutRes int resource, @Nullable ViewGroup root) {
return inflate(resource, root, root != null);
}
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();
}
}
复制代码通过资源大管家，也就是Resources来加载layout文件，最后通过inflate方法的一步步调用，会走到createViewFromTag方法，该方法内部会对每个标签生成对应的View对象。
View createViewFromTag(View parent, String name, Context context, AttributeSet attrs,
boolean ignoreThemeAttr) {
...
try {
View view;
if (mFactory2 != null) {
//注释1
view = mFactory2.onCreateView(parent, name, context, attrs);
}
...
if (view == null && mPrivateFactory != null) {
view = mPrivateFactory.onCreateView(parent, name, context, attrs);
}
//注释2
if (view == null) {
final Object lastContext = mConstructorArgs[0];
mConstructorArgs[0] = context;
try {
if (-1 == name.indexOf('.')) {
view = onCreateView(parent, name, attrs);
} else {
view = createView(name, null, attrs);
}
} finally {
mConstructorArgs[0] = lastContext;
}
}
return view;
} catch (InflateException e) {
throw e;
} catch (ClassNotFoundException e) {
final InflateException ie = new InflateException(attrs.getPositionDescription()
+ ": Error inflating class " + name, e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} catch (Exception e) {
final InflateException ie = new InflateException(attrs.getPositionDescription()
+ ": Error inflating class " + name, e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
}
}
复制代码经过一些列调用进入注释2处，通过mFactory2的onCreateView方法创建对应的View对象，mFactory2的赋值时机需要我们回到MainActivity代码中进行一步步查看：
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
复制代码进入AppCompatActivity的onCreate方法中：
protected void onCreate(@Nullable Bundle savedInstanceState) {
final AppCompatDelegate delegate = getDelegate();
//注释1
delegate.installViewFactory();
delegate.onCreate(savedInstanceState);
...
super.onCreate(savedInstanceState);
}
复制代码注释1处调用了delegate的installViewFactory方法，这个delegate对象是通过getDelegate()方法：
@NonNull
public AppCompatDelegate getDelegate() {
if (mDelegate == null) {
mDelegate = AppCompatDelegate.create(this, this);
}
return mDelegate;
}
复制代码这段代码应该很熟悉了吧，也就是说最终调用AppCompatDelegateImplV9的installViewFactory方法，查看源码：
class AppCompatDelegateImplV9 extends AppCompatDelegateImplBase
implements MenuBuilder.Callback, LayoutInflater.Factory2 {
...
@Override
public void installViewFactory() {
LayoutInflater layoutInflater = LayoutInflater.from(mContext);
if (layoutInflater.getFactory() == null) {
//注释1
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");
}
}
}
...
}
复制代码AppCompatDelegateImplV9本身也实现了LayoutInflater.Factory2接口，在注释1处调用LayoutInflaterCompat的setFactory2方法并传入layoutInflater实例以及自身AppCompatDelegateImplV9对象。
进入LayoutInflaterCompat的setFactory2方法：
public void setFactory2(LayoutInflater inflater, LayoutInflater.Factory2 factory) {
//注释1
inflater.setFactory2(factory);
final LayoutInflater.Factory f = inflater.getFactory();
if (f instanceof LayoutInflater.Factory2) {
forceSetFactory2(inflater, (LayoutInflater.Factory2) f);
} else {
// Else, we will force set the original wrapped Factory2
forceSetFactory2(inflater, factory);
}
}
复制代码注释1处将getDelegate()方法获取到的AppCompatDelegate对象（具体实现类是AppCompatDelegateImplV9）通过inflater的setFactory2传入进去。
进入LayoutInflater的setFactory2：
public void setFactory2(Factory2 factory) {
if (mFactorySet) {
throw new IllegalStateException("A factory has already been set on this LayoutInflater");
}
if (factory == null) {
throw new NullPointerException("Given factory can not be null");
}
mFactorySet = true;
if (mFactory == null) {
mFactory = mFactory2 = factory;
} else {
mFactory = mFactory2 = new FactoryMerger(factory, factory, mFactory, mFactory2);
}
}
复制代码到这里我们知道了LayoutInflater的成员变量mFactory2就是AppCompatDelegateImplV9对象（AppCompatDelegateImplV9实现LayoutInflater.Factory2接口）。
继续回到createViewFromTag方法中：
View createViewFromTag(View parent, String name, Context context, AttributeSet attrs,
boolean ignoreThemeAttr) {
...
try {
View view;
if (mFactory2 != null) {
//注释1
view = mFactory2.onCreateView(parent, name, context, attrs);
}
...
if (view == null && mPrivateFactory != null) {
view = mPrivateFactory.onCreateView(parent, name, context, attrs);
}
//注释2
if (view == null) {
final Object lastContext = mConstructorArgs[0];
mConstructorArgs[0] = context;
try {
if (-1 == name.indexOf('.')) {
view = onCreateView(parent, name, attrs);
} else {
view = createView(name, null, attrs);
}
} finally {
mConstructorArgs[0] = lastContext;
}
}
return view;
} catch (InflateException e) {
throw e;
} catch (ClassNotFoundException e) {
final InflateException ie = new InflateException(attrs.getPositionDescription()
+ ": Error inflating class " + name, e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} catch (Exception e) {
final InflateException ie = new InflateException(attrs.getPositionDescription()
+ ": Error inflating class " + name, e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
}
}
复制代码注释1处调用mFactory2的onCreateView方法，也就是调用AppCompatDelegateImplV9的onCreateView方法。
进入AppCompatDelegateImplV9的onCreateView方法：
@Override
public final View onCreateView(View parent, String name, Context context, AttributeSet attrs) {
...
return createView(parent, name, context, attrs);
}
复制代码进入AppCompatDelegateImplV9的createView方法
@Override
public View createView(View parent, final String name, @NonNull Context context,
@NonNull AttributeSet attrs) {
...
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 */
);
}
复制代码调用mAppCompatViewInflater的createView方法，继续进入：
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;
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;
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;
}
复制代码整个调用流程图如下：
mAppCompatViewInflater的createView方法主要通过switch/case形式对相应的标签名字创建对应的View对象，比如TextView调用createTextView方法创建TextView对象。这里有个问题，如果是自定义的View或是在这里并没有判断的View的话，View就为null。
继续回到createViewFromTag方法中：
View createViewFromTag(View parent, String name, Context context, AttributeSet attrs,
boolean ignoreThemeAttr) {
...
try {
View view;
if (mFactory2 != null) {
//注释1
view = mFactory2.onCreateView(parent, name, context, attrs);
}
...
if (view == null && mPrivateFactory != null) {
view = mPrivateFactory.onCreateView(parent, name, context, attrs);
}
//注释2
if (view == null) {
final Object lastContext = mConstructorArgs[0];
mConstructorArgs[0] = context;
try {
if (-1 == name.indexOf('.')) {
//注释3
view = onCreateView(parent, name, attrs);
} else {
//注释4
view = createView(name, null, attrs);
}
} finally {
mConstructorArgs[0] = lastContext;
}
}
return view;
} catch (InflateException e) {
throw e;
} catch (ClassNotFoundException e) {
final InflateException ie = new InflateException(attrs.getPositionDescription()
+ ": Error inflating class " + name, e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} catch (Exception e) {
final InflateException ie = new InflateException(attrs.getPositionDescription()
+ ": Error inflating class " + name, e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
}
}
复制代码注释1处在上面已经解析过了就是对layout文件中的标签类型创建对应的View对象，如果是自定义的View或是layout文件中相应的View标签在这里并没有判断（毕竟系统不可能全部都判断到），这时View就为null。进入注释2处对View为null的情况进行处理。
注释3处如果不是全限定名的类名调用onCreateView方法：
protected View onCreateView(View parent, String name, AttributeSet attrs)
throws ClassNotFoundException {
return onCreateView(name, attrs);
}
protected View onCreateView(String name, AttributeSet attrs)
throws ClassNotFoundException {
return createView(name, "android.view.", attrs);
}
复制代码如果不是全限定的类名，默认加上“android.view.”。
继续往下追踪：
public final View createView(String name, String prefix, AttributeSet attrs)
throws ClassNotFoundException, InflateException {
Constructor<? extends View> constructor = sConstructorMap.get(name);
if (constructor != null && !verifyClassLoader(constructor)) {
constructor = null;
sConstructorMap.remove(name);
}
Class<? extends View> clazz = null;
try {
Trace.traceBegin(Trace.TRACE_TAG_VIEW, name);
if (constructor == null) {
// Class not found in the cache, see if it's real, and try to add it
clazz = mContext.getClassLoader().loadClass(
prefix != null ? (prefix + name) : name).asSubclass(View.class);
if (mFilter != null && clazz != null) {
boolean allowed = mFilter.onLoadClass(clazz);
if (!allowed) {
failNotAllowed(name, prefix, attrs);
}
}
constructor = clazz.getConstructor(mConstructorSignature);
constructor.setAccessible(true);
sConstructorMap.put(name, constructor);
} else {
// If we have a filter, apply it to cached constructor
if (mFilter != null) {
// Have we seen this name before?
Boolean allowedState = mFilterMap.get(name);
if (allowedState == null) {
// New class -- remember whether it is allowed
clazz = mContext.getClassLoader().loadClass(
prefix != null ? (prefix + name) : name).asSubclass(View.class);
boolean allowed = clazz != null && mFilter.onLoadClass(clazz);
mFilterMap.put(name, allowed);
if (!allowed) {
failNotAllowed(name, prefix, attrs);
}
} else if (allowedState.equals(Boolean.FALSE)) {
failNotAllowed(name, prefix, attrs);
}
}
}
Object lastContext = mConstructorArgs[0];
if (mConstructorArgs[0] == null) {
// Fill in the context if not already within inflation.
mConstructorArgs[0] = mContext;
}
Object[] args = mConstructorArgs;
args[1] = attrs;
//注释1
final View view = constructor.newInstance(args);
if (view instanceof ViewStub) {
// Use the same context when inflating ViewStub later.
final ViewStub viewStub = (ViewStub) view;
viewStub.setLayoutInflater(cloneInContext((Context) args[0]));
}
mConstructorArgs[0] = lastContext;
return view;
} catch (NoSuchMethodException e) {
final InflateException ie = new InflateException(attrs.getPositionDescription()
+ ": Error inflating class " + (prefix != null ? (prefix + name) : name), e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} catch (ClassCastException e) {
// If loaded class is not a View subclass
final InflateException ie = new InflateException(attrs.getPositionDescription()
+ ": Class is not a View " + (prefix != null ? (prefix + name) : name), e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} catch (ClassNotFoundException e) {
// If loadClass fails, we should propagate the exception.
throw e;
} catch (Exception e) {
final InflateException ie = new InflateException(
attrs.getPositionDescription() + ": Error inflating class "
+ (clazz == null ? "<unknown>" : clazz.getName()), e);
ie.setStackTrace(EMPTY_STACK_TRACE);
throw ie;
} finally {
Trace.traceEnd(Trace.TRACE_TAG_VIEW);
}
}
复制代码上面代码比较多，总结就是在注释1处通过反射创建相应的View对象。
到这里我们知道了Layout资源文件的加载是通过LayoutInflater.Factory2的onCreateView方法实现的。也就是如果我们自己定义一个实现了LayoutInflater.Factory2接口的类并实现onCreateView方法，在该方法中保存需要换肤的View，最后给换肤的View设置插件中的资源。
加载外部资源可以通过反射创建AssetManager对象，反射调用AssetManager的addAssetPath方法加载外部资源，最后创建Resources对象并传入刚创建的AssetManager对象，通过刚创建的Resources对象获取相应的资源。
首先获取需要换肤的View，怎么知道哪些View需要换肤，可以通过自定义属性来判断，新建attr.xml：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="Skin">
<attr name="skinChange" format="boolean" />
</declare-styleable>
</resources>
复制代码skinChange用于判断View是否需要进行换肤。编写我们的布局文件：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:skinChange="true"
android:background="@drawable/girl"
android:orientation="vertical">
<Button
android:id="@+id/btn_skin"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@color/text_color"
app:skinChange="true"
android:text="点击进行换肤"
tools:ignore="MissingPrefix" />
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:skinChange="true"
android:textSize="15sp"
android:textColor="@color/text_color"
android:text="这是一段文本，当点击进行换肤时，颜色会进行相应的变化"
tools:ignore="MissingPrefix" />
<ImageView
android:layout_width="100dp"
android:layout_height="100dp"
app:skinChange="true"
android:src="@drawable/level"
android:layout_marginTop="10dp"
tools:ignore="MissingPrefix" />
</LinearLayout>
复制代码新建SkinFactory类并实现自LayoutInflater.Factory2接口：
public class SkinFactory implements LayoutInflater.Factory2 {
public class SkinFactory implements LayoutInflater.Factory2 {
private AppCompatDelegate mDelegate;
static final Class<?>[] mConstructorSignature = new Class[]{Context.class, AttributeSet.class};//
final Object[] mConstructorArgs = new Object[2];
private static final HashMap<String, Constructor<? extends View>> sConstructorMap = new HashMap<String, Constructor<? extends View>>();
static final String[] prefix = new String[]{
"android.widget.",
"android.view.",
"android.webkit."
};
public void setDelegate(AppCompatDelegate delegate) {
this.mDelegate = delegate;
}
@Override
public View onCreateView(String name, Context context, AttributeSet attrs) {
return null;
}
@Override
public View onCreateView(View parent, String name, Context context, AttributeSet attrs) {
View view = mDelegate.createView(parent, name, context, attrs);
if (view == null) {
mConstructorArgs[0] = context;
try {
if (-1 == name.indexOf('.')) {
view = createViewByPrefix(context, name, prefix, attrs);
} else {
view = createViewByPrefix(context, name, null, attrs);
}
} catch (Exception e) {
e.printStackTrace();
}
}
//保存需要换肤的View
SkinChange.getInstance().saveSkin(context, attrs, view);
return view;
}
private View createViewByPrefix(Context context, String name, String[] prefixs, AttributeSet attrs) {
Constructor<? extends View> constructor = sConstructorMap.get(name);
Class<? extends View> clazz = null;
if (constructor == null) {
try {
if (prefixs != null && prefixs.length > 0) {
for (String prefix : prefixs) {
clazz = context.getClassLoader().loadClass(
prefix != null ? (prefix + name) : name).asSubclass(View.class);
if (clazz != null) break;
}
} else {
clazz = context.getClassLoader().loadClass(name).asSubclass(View.class);
}
if (clazz == null) {
return null;
}
constructor = clazz.getConstructor(mConstructorSignature);
} catch (Exception e) {
e.printStackTrace();
return null;
}
constructor.setAccessible(true);
//缓存
sConstructorMap.put(name, constructor);
}
Object[] args = mConstructorArgs;
args[1] = attrs;
try {
//通过反射创建View对象
return constructor.newInstance(args);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
}
复制代码Factory2的onCreateView的实现的逻辑与源码差不多，通过系统的AppCompatDelegate的createView方法创建View，如果创建的View为空，通过反射创建View对象，最主要的一步是SkinChange.getInstance().saveSkin方法，用于保存换肤的View，具体代码如下，新建SkinChange类：
public class SkinChange {
private SkinChange(){}
public static SkinChange getInstance(){
return Holder.SKIN_CHANGE;
}
private static class Holder{
private static final SkinChange SKIN_CHANGE=new SkinChange();
}
private List<SkinChange.Skin> mSkinListView = new ArrayList<>();
public List<SkinChange.Skin> getSkinViewList(){
return mSkinListView;
}
public void saveSkin(Context context, AttributeSet attrs, View view) {
TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.Skin);
boolean skin = a.getBoolean(R.styleable.Skin_skinChange, false);
if (skin) {
final int Len = attrs.getAttributeCount();
HashMap<String, String> attrMap = new HashMap<>();
for (int i = 0; i < Len; i++) {
String attrName = attrs.getAttributeName(i);
String attrValue = attrs.getAttributeValue(i);
attrMap.put(attrName, attrValue);
Log.d("saveSkin","attrName="+attrName+" attrValue="+attrValue);
}
SkinChange.Skin skinView = new SkinChange.Skin();
skinView.view = view;
skinView.attrsMap = attrMap;
mSkinListView.add(skinView);
}
}
public static class Skin{
View view;
HashMap<String, String> attrsMap;
}
}
复制代码将属性skinChange为true的View以及它的所有属性保存起来。
新建BaseActivity，实现onCreate方法，在setContentView方法之前替换LayoutInflater的成员变量mFactory2：
public abstract class BaseActivity extends AppCompatActivity {
private SkinFactory mSkinFactory;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
if(null == mSkinFactory){
mSkinFactory=new SkinFactory();
}
mSkinFactory.setDelegate(getDelegate());
LayoutInflater layoutInflater=LayoutInflater.from(this);
layoutInflater.setFactory2(mSkinFactory);
super.onCreate(savedInstanceState);
}
}
复制代码运行效果如下：
从控制台打印的信息我们已经知道哪些View的属性需要进行换肤，剩下的就是加载外部apk中的资源，创建LoadResources类：
public class LoadResources {
private Resources mSkinResources;
private Context mContext;
private String mOutPkgName;
public static LoadResources getInstance() {
return Holder.LOAD_RESOURCES;
}
private LoadResources() {
}
private static class Holder{
private static final LoadResources LOAD_RESOURCES=new LoadResources();
}
public void init(Context context) {
mContext = context.getApplicationContext();
}
public void load(final String path) {
File file = new File(path);
if (!file.exists()) {
return;
}
PackageManager mPm = mContext.getPackageManager();
PackageInfo mInfo = mPm.getPackageArchiveInfo(path, PackageManager.GET_ACTIVITIES);
mOutPkgName = mInfo.packageName;
AssetManager assetManager;
try {
assetManager = AssetManager.class.newInstance();
Method addAssetPath = assetManager.getClass().getMethod("addAssetPath", String.class);
addAssetPath.invoke(assetManager, path);
mSkinResources = new Resources(assetManager,
mContext.getResources().getDisplayMetrics(),
mContext.getResources().getConfiguration());
} catch (Exception e) {
e.printStackTrace();
}
}
public int getColor(int resId) {
if (mSkinResources == null) {
return resId;
}
String resName = mSkinResources.getResourceEntryName(resId);
int outResId = mSkinResources.getIdentifier(resName, "color", mOutPkgName);
if (outResId == 0) {
return resId;
}
return mSkinResources.getColor(outResId);
}
public Drawable getDrawable(int resId) {
if (mSkinResources == null) {
return ContextCompat.getDrawable(mContext, resId);
}
String resName = mSkinResources.getResourceEntryName(resId);
int outResId = mSkinResources.getIdentifier(resName, "drawable", mOutPkgName);
if (outResId == 0) {
return ContextCompat.getDrawable(mContext, resId);
}
return mSkinResources.getDrawable(outResId);
}
}
复制代码LoadResources类非常简单，通过反射创建AssetManager，并执行addAssetPath来加载外部apk，最后创建一个外部资源的Resources。
新建接口ISkinView用于约定换肤方法：
public interface ISkinView {
void change(String path);
}
复制代码创建SkinChangeBiz并实现ISkinView接口：
public class SkinChangeBiz implements ISkinView {
private static class Holder {
private static final ISkinView SKIN_CHANGE_BIZ = new SkinChangeBiz();
}
public static ISkinView getInstance() {
return Holder.SKIN_CHANGE_BIZ;
}
@Override
public void change(String path) {
File skinFile = new File(Environment.getExternalStorageDirectory(), path);
LoadResources.getInstance().load(skinFile.getAbsolutePath());
for (SkinChange.Skin skinView : SkinChange.getInstance().getSkinViewList()) {
changeSkin(skinView);
}
}
void changeSkin(SkinChange.Skin skinView) {
if (!TextUtils.isEmpty(skinView.attrsMap.get("background"))) {
int bgId = Integer.parseInt(skinView.attrsMap.get("background").substring(1));
String attrType = skinView.view.getResources().getResourceTypeName(bgId);
if (TextUtils.equals(attrType, "drawable")) {
skinView.view.setBackgroundDrawable(LoadResources.getInstance().getDrawable(bgId));
} else if (TextUtils.equals(attrType, "color")) {
skinView.view.setBackgroundColor(LoadResources.getInstance().getColor(bgId));
}
}
if (skinView.view instanceof TextView) {
if (!TextUtils.isEmpty(skinView.attrsMap.get("textColor"))) {
int textColorId = Integer.parseInt(skinView.attrsMap.get("textColor").substring(1));
((TextView) skinView.view).setTextColor(LoadResources.getInstance().getColor(textColorId));
}
}
}
}
复制代码SkinChangeBiz的change方法中先加载外部资源，再遍历之前保存的换肤View，对相关属性进行设置。
前期工作已经准备好了，剩下的创建皮肤插件，新建工程，添加需要换肤的资源，注意资源名必须与宿主的资源名一样，皮肤插件的sdk版本也必须保持一致，皮肤插件工程就不贴出来了，比较简单。
mBtnSkin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//进行换肤
SkinChangeBiz.getInstance().change("skinPlugin.apk");
}
});
复制代码运行效果如下：
github地址请点击这里