深入浅出换肤相关技术以及如何实现-白红宇

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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
     constructor = sConstructorMap.get(name);        if (constructor != null && !verifyClassLoader(constructor)) {            constructor = null;            sConstructorMap.remove(name);        }        Class
     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 ? "
    
     " : 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：

skinChange用于判断View是否需要进行换肤。编写我们的布局文件：

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
    
     > sConstructorMap = new HashMap
     
      >();    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
       constructor = sConstructorMap.get(name);        Class
       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
    
      mSkinListView = new ArrayList<>();    public List
     
       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
      
        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
       
         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：

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