手册   游戏   WEB   字典   单词   在线工具  

深入浅出换肤相关技术以及如何实现

温馨提示: 阅读本文需要 60-70 分钟

微信公众号: 顾林海

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:

  1. public class MainActivity extends AppCompatActivity {
  2.     @Override
  3.     protected void onCreate(@Nullable Bundle savedInstanceState) {
  4.         super.onCreate(savedInstanceState);
  5.         setContentView(R.layout.activity_main);
  6.     }
  7. }

MainActivity 继承自 AppCompatActivity,AppCompatActivity 是 Android Support Library 包下的类, 点击进入 AppCompatActivity 的 setContentView 方法:

  1. @Override
  2.     public void setContentView(@LayoutRes int layoutResID) {
  3.         getDelegate().setContentView(layoutResID);
  4.     }

通过 getDelegate()方法返回一个 AppCompatDelegate 对象, 并调用 AppCompatDelegate 对象的 setContentView 方法.

  1. @NonNull
  2.     public AppCompatDelegate getDelegate() {
  3.         if (mDelegate == null) {
  4.             mDelegate = AppCompatDelegate.create(this, this);
  5.         }
  6.         return mDelegate;
  7.     }

通过 AppCompatDelegate 的 create 方法创建 AppCompatDelegate 对象:

  1. public static AppCompatDelegate create(Activity activity, AppCompatCallback callback) {
  2.         return create(activity, activity.getWindow(), callback);
  3.     }

通过 create 方法返回 AppCompatDelegate 对象:

  1. private static AppCompatDelegate create(Context context, Windows Windows,
  2.             AppCompatCallback callback) {
  3.         if (Build.VERSION.SDK_INT>= 24) {
  4.             return new AppCompatDelegateImplN(context, Windows, callback);
  5.         } else if (Build.VERSION.SDK_INT>= 23) {
  6.             return new AppCompatDelegateImplV23(context, Windows, callback);
  7.         } else {
  8.             return new AppCompatDelegateImplV14(context, Windows, callback);
  9.         }
  10.     }

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:

  1. @Override
  2.     public void setContentView(@LayoutRes int layoutResID) {
  3.         getDelegate().setContentView(layoutResID);
  4.     }

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:

  1. //Android.support.v7.App.AppCompatDelegateImplV9
  2.     @Override
  3.     public void setContentView(int resId) {
  4.         ensureSubDecor();
  5.         ViewGroup contentParent = (ViewGroup) mSubDecor.findViewById(Android.R.id.content);
  6.         contentParent.removeAllViews();
  7.         // 注释 1
  8.         LayoutInflater.from(mContext).inflate(resId, contentParent);
  9.         mOriginalWindowCallback.onContentChanged();
  10.     }

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.

  1. public View inflate(@LayoutRes int resource, @Nullable ViewGroup root) {
  2.         return inflate(resource, root, root != null);
  3.     }
  4.     public View inflate(@LayoutRes int resource, @Nullable ViewGroup root, boolean attachToRoot) {
  5.         final Resources res = getContext().getResources();
  6.         if (DEBUG) {
  7.             Log.d(TAG, "INFLATING from resource: \"" + res.getResourceName(resource) + "\" ("                    + Integer.toHexString(resource) +")");
  8.         }
  9.         final XmlResourceParser parser = res.getLayout(resource);
  10.         try {
  11.             return inflate(parser, root, attachToRoot);
  12.         } finally {
  13.             parser.close();
  14.         }
  15.     }

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.

  1. View createViewFromTag(View parent, String name, Context context, AttributeSet attrs,
  2.             boolean ignoreThemeAttr) {
  3.         ...
  4.         try {
  5.             View view;
  6.             if (mFactory2 != null) {
  7.                 // 注释 1
  8.                 view = mFactory2.onCreateView(parent, name, context, attrs);
  9.             }
  10.             ...
  11.             if (view == null && mPrivateFactory != null) {
  12.                 view = mPrivateFactory.onCreateView(parent, name, context, attrs);
  13.             }
  14.             // 注释 2
  15.             if (view == null) {
  16.                 final Object lastContext = mConstructorArgs[0];
  17.                 mConstructorArgs[0] = context;
  18.                 try {
  19.                     if (-1 == name.indexOf('.')) {
  20.                         view = onCreateView(parent, name, attrs);
  21.                     } else {
  22.                         view = createView(name, null, attrs);
  23.                     }
  24.                 } finally {
  25.                     mConstructorArgs[0] = lastContext;
  26.                 }
  27.             }
  28.             return view;
  29.         } catch (InflateException e) {
  30.             throw e;
  31.         } catch (ClassNotFoundException e) {
  32.             final InflateException IE = new InflateException(attrs.getPositionDescription()
  33.                     + ": Error inflating class" + name, e);
  34.             IE.setStackTrace(EMPTY_STACK_TRACE);
  35.             throw IE;
  36.         } catch (Exception e) {
  37.             final InflateException IE = new InflateException(attrs.getPositionDescription()
  38.                     + ": Error inflating class" + name, e);
  39.             IE.setStackTrace(EMPTY_STACK_TRACE);
  40.             throw IE;
  41.         }
  42.     }

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:

  1. public class MainActivity extends AppCompatActivity {
  2.     @Override
  3.     protected void onCreate(@Nullable Bundle savedInstanceState) {
  4.         super.onCreate(savedInstanceState);
  5.         setContentView(R.layout.activity_main);
  6.     }
  7. }

进入 AppCompatActivity 的 onCreate 方法中:

  1. protected void onCreate(@Nullable Bundle savedInstanceState) {
  2.         final AppCompatDelegate delegate = getDelegate();
  3.         // 注释 1
  4.         delegate.installViewFactory();
  5.         delegate.onCreate(savedInstanceState);
  6.         ...
  7.         super.onCreate(savedInstanceState);
  8.     }

注释 1 处调用了 delegate 的 installViewFactory 方法, 这个 delegate 对象是通过 getDelegate()方法:

  1. @NonNull
  2.     public AppCompatDelegate getDelegate() {
  3.         if (mDelegate == null) {
  4.             mDelegate = AppCompatDelegate.create(this, this);
  5.         }
  6.         return mDelegate;
  7.     }

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:

  1. class AppCompatDelegateImplV9 extends AppCompatDelegateImplBase
  2.         implements MenuBuilder.Callback, LayoutInflater.Factory2 {
  3.     ...
  4.     @Override
  5.     public void installViewFactory() {
  6.         LayoutInflater layoutInflater = LayoutInflater.from(mContext);
  7.         if (layoutInflater.getFactory() == null) {
  8.             // 注释 1
  9.             LayoutInflaterCompat.setFactory2(layoutInflater, this);
  10.         } else {
  11.             if (!(layoutInflater.getFactory2() instanceof AppCompatDelegateImplV9)) {
  12.                 Log.i(TAG, "The Activity's LayoutInflater already has a Factory installed"                        +" so we can not install AppCompat's");
  13.             }
  14.         }
  15.     }
  16.     ...
  17. }

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:

  1. public void setFactory2(LayoutInflater inflater, LayoutInflater.Factory2 factory) {
  2.             // 注释 1
  3.             inflater.setFactory2(factory);
  4.             final LayoutInflater.Factory f = inflater.getFactory();
  5.             if (f instanceof LayoutInflater.Factory2) {
  6.                 forceSetFactory2(inflater, (LayoutInflater.Factory2) f);
  7.             } else {
  8.                 // Else, we will force set the original wrapped Factory2
  9.                 forceSetFactory2(inflater, factory);
  10.             }
  11.         }

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:

  1. public void setFactory2(Factory2 factory) {
  2.         if (mFactorySet) {
  3.             throw new IllegalStateException("A factory has already been set on this LayoutInflater");
  4.         }
  5.         if (factory == null) {
  6.             throw new NullPointerException("Given factory can not be null");
  7.         }
  8.         mFactorySet = true;
  9.         if (mFactory == null) {
  10.             mFactory = mFactory2 = factory;
  11.         } else {
  12.             mFactory = mFactory2 = new FactoryMerger(factory, factory, mFactory, mFactory2);
  13.         }
  14.     }

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:

  1. View createViewFromTag(View parent, String name, Context context, AttributeSet attrs,
  2.             boolean ignoreThemeAttr) {
  3.         ...
  4.         try {
  5.             View view;
  6.             if (mFactory2 != null) {
  7.                 // 注释 1
  8.                 view = mFactory2.onCreateView(parent, name, context, attrs);
  9.             }
  10.             ...
  11.             if (view == null && mPrivateFactory != null) {
  12.                 view = mPrivateFactory.onCreateView(parent, name, context, attrs);
  13.             }
  14.             // 注释 2
  15.             if (view == null) {
  16.                 final Object lastContext = mConstructorArgs[0];
  17.                 mConstructorArgs[0] = context;
  18.                 try {
  19.                     if (-1 == name.indexOf('.')) {
  20.                         view = onCreateView(parent, name, attrs);
  21.                     } else {
  22.                         view = createView(name, null, attrs);
  23.                     }
  24.                 } finally {
  25.                     mConstructorArgs[0] = lastContext;
  26.                 }
  27.             }
  28.             return view;
  29.         } catch (InflateException e) {
  30.             throw e;
  31.         } catch (ClassNotFoundException e) {
  32.             final InflateException IE = new InflateException(attrs.getPositionDescription()
  33.                     + ": Error inflating class" + name, e);
  34.             IE.setStackTrace(EMPTY_STACK_TRACE);
  35.             throw IE;
  36.         } catch (Exception e) {
  37.             final InflateException IE = new InflateException(attrs.getPositionDescription()
  38.                     + ": Error inflating class" + name, e);
  39.             IE.setStackTrace(EMPTY_STACK_TRACE);
  40.             throw IE;
  41.         }
  42.     }

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:

  1. @Override
  2.     public final View onCreateView(View parent, String name, Context context, AttributeSet attrs) {
  3.         ...
  4.         return createView(parent, name, context, attrs);
  5.     }

进入 AppCompatDelegateImplV9 的 createView 方法

  1. @Override
  2.     public View createView(View parent, final String name, @NonNull Context context,
  3.             @NonNull AttributeSet attrs) {
  4.         ...
  5.         return mAppCompatViewInflater.createView(parent, name, context, attrs, inheritContext,
  6.                 IS_PRE_LOLLIPOP, /* Only read Android:theme pre-L (L+ handles this anyway) */
  7.                 true, /* Read read App:theme as a fallback at all times for legacy reasons */
  8.                 VectorEnabledTintResources.shouldBeUsed() /* Only tint wrap the context if enabled */
  9.         );
  10.     }

调用 mAppCompatViewInflater 的 createView 方法, 继续进入:

  1. final View createView(View parent, final String name, @NonNull Context context,
  2.             @NonNull AttributeSet attrs, boolean inheritContext,
  3.             boolean readAndroidTheme, boolean readAppTheme, boolean wrapContext) {
  4.         final Context originalContext = context;
  5.         if (inheritContext && parent != null) {
  6.             context = parent.getContext();
  7.         }
  8.         if (readAndroidTheme || readAppTheme) {
  9.             // We then apply the theme on the context, if specified
  10.             context = themifyContext(context, attrs, readAndroidTheme, readAppTheme);
  11.         }
  12.         if (wrapContext) {
  13.             context = TintContextWrapper.wrap(context);
  14.         }
  15.         View view = null;
  16.         // We need to 'inject' our tint aware Views in place of the standard framework versions
  17.         switch (name) {
  18.             case "TextView":
  19.                 view = createTextView(context, attrs);
  20.                 verifyNotNull(view, name);
  21.                 break;
  22.             case "ImageView":
  23.                 view = createImageView(context, attrs);
  24.                 verifyNotNull(view, name);
  25.                 break;
  26.             case "Button":
  27.                 view = createButton(context, attrs);
  28.                 verifyNotNull(view, name);
  29.                 break;
  30.             case "EditText":
  31.                 view = createEditText(context, attrs);
  32.                 verifyNotNull(view, name);
  33.                 break;
  34.             case "Spinner":
  35.                 view = createSpinner(context, attrs);
  36.                 verifyNotNull(view, name);
  37.                 break;
  38.             case "ImageButton":
  39.                 view = createImageButton(context, attrs);
  40.                 verifyNotNull(view, name);
  41.                 break;
  42.             case "CheckBox":
  43.                 view = createCheckBox(context, attrs);
  44.                 verifyNotNull(view, name);
  45.                 break;
  46.             case "RadioButton":
  47.                 view = createRadioButton(context, attrs);
  48.                 verifyNotNull(view, name);
  49.                 break;
  50.             case "CheckedTextView":
  51.                 view = createCheckedTextView(context, attrs);
  52.                 verifyNotNull(view, name);
  53.                 break;
  54.             case "AutoCompleteTextView":
  55.                 view = createAutoCompleteTextView(context, attrs);
  56.                 verifyNotNull(view, name);
  57.                 break;
  58.             case "MultiAutoCompleteTextView":
  59.                 view = createMultiAutoCompleteTextView(context, attrs);
  60.                 verifyNotNull(view, name);
  61.                 break;
  62.             case "RatingBar":
  63.                 view = createRatingBar(context, attrs);
  64.                 verifyNotNull(view, name);
  65.                 break;
  66.             case "SeekBar":
  67.                 view = createSeekBar(context, attrs);
  68.                 verifyNotNull(view, name);
  69.                 break;
  70.             default:
  71.                 // The fallback that allows extending class to take over view inflation
  72.                 // for other tags. Note that we don't check that the result is not-null.
  73.                 // That allows the custom inflater path to fall back on the default one
  74.                 // later in this method.
  75.                 view = createView(context, name, attrs);
  76.         }
  77.         if (view == null && originalContext != context) {
  78.             // If the original context does not equal our themed context, then we need to manually
  79.             // inflate it using the name so that Android:theme takes effect.
  80.             view = createViewFromTag(context, name, attrs);
  81.         }
  82.         if (view != null) {
  83.             // If we have created a view, check its Android:onClick
  84.             checkOnClickListener(view, attrs);
  85.         }
  86.         return view;
  87.     }

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:

  1. View createViewFromTag(View parent, String name, Context context, AttributeSet attrs,
  2.             boolean ignoreThemeAttr) {
  3.         ...
  4.         try {
  5.             View view;
  6.             if (mFactory2 != null) {
  7.                 // 注释 1
  8.                 view = mFactory2.onCreateView(parent, name, context, attrs);
  9.             }
  10.             ...
  11.             if (view == null && mPrivateFactory != null) {
  12.                 view = mPrivateFactory.onCreateView(parent, name, context, attrs);
  13.             }
  14.             // 注释 2
  15.             if (view == null) {
  16.                 final Object lastContext = mConstructorArgs[0];
  17.                 mConstructorArgs[0] = context;
  18.                 try {
  19.                     if (-1 == name.indexOf('.')) {
  20.                         // 注释 3
  21.                         view = onCreateView(parent, name, attrs);
  22.                     } else {
  23.                         // 注释 4
  24.                         view = createView(name, null, attrs);
  25.                     }
  26.                 } finally {
  27.                     mConstructorArgs[0] = lastContext;
  28.                 }
  29.             }
  30.             return view;
  31.         } catch (InflateException e) {
  32.             throw e;
  33.         } catch (ClassNotFoundException e) {
  34.             final InflateException IE = new InflateException(attrs.getPositionDescription()
  35.                     + ": Error inflating class" + name, e);
  36.             IE.setStackTrace(EMPTY_STACK_TRACE);
  37.             throw IE;
  38.         } catch (Exception e) {
  39.             final InflateException IE = new InflateException(attrs.getPositionDescription()
  40.                     + ": Error inflating class" + name, e);
  41.             IE.setStackTrace(EMPTY_STACK_TRACE);
  42.             throw IE;
  43.         }
  44.     }

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:

  1. protected View onCreateView(View parent, String name, AttributeSet attrs)
  2.             throws ClassNotFoundException {
  3.         return onCreateView(name, attrs);
  4.     }
  5.     protected View onCreateView(String name, AttributeSet attrs)
  6.             throws ClassNotFoundException {
  7.         return createView(name, "android.view.", attrs);
  8.     }

如果不是全限定的类名, 默认加上 "android.view.".

继续往下追踪:

  1. public final View createView(String name, String prefix, AttributeSet attrs)
  2.             throws ClassNotFoundException, InflateException {
  3.         Constructor<? extends View> constructor = sConstructorMap.get(name);
  4.         if (constructor != null && !verifyClassLoader(constructor)) {
  5.             constructor = null;
  6.             sConstructorMap.remove(name);
  7.         }
  8.         Class<? extends View> clazz = null;
  9.         try {
  10.             Trace.traceBegin(Trace.TRACE_TAG_VIEW, name);
  11.             if (constructor == null) {
  12.                 // Class not found in the cache, see if it's real, and try to add it
  13.                 clazz = mContext.getClassLoader().loadClass(
  14.                         prefix != null ? (prefix + name) : name).asSubclass(View.class);
  15.                 if (mFilter != null && clazz != null) {
  16.                     boolean allowed = mFilter.onLoadClass(clazz);
  17.                     if (!allowed) {
  18.                         failNotAllowed(name, prefix, attrs);
  19.                     }
  20.                 }
  21.                 constructor = clazz.getConstructor(mConstructorSignature);
  22.                 constructor.setAccessible(true);
  23.                 sConstructorMap.put(name, constructor);
  24.             } else {
  25.                 // If we have a filter, apply it to cached constructor
  26.                 if (mFilter != null) {
  27.                     // Have we seen this name before?
  28.                     Boolean allowedState = mFilterMap.get(name);
  29.                     if (allowedState == null) {
  30.                         // New class -- remember whether it is allowed
  31.                         clazz = mContext.getClassLoader().loadClass(
  32.                                 prefix != null ? (prefix + name) : name).asSubclass(View.class);
  33.                         boolean allowed = clazz != null && mFilter.onLoadClass(clazz);
  34.                         mFilterMap.put(name, allowed);
  35.                         if (!allowed) {
  36.                             failNotAllowed(name, prefix, attrs);
  37.                         }
  38.                     } else if (allowedState.equals(Boolean.FALSE)) {
  39.                         failNotAllowed(name, prefix, attrs);
  40.                     }
  41.                 }
  42.             }
  43.             Object lastContext = mConstructorArgs[0];
  44.             if (mConstructorArgs[0] == null) {
  45.                 // Fill in the context if not already within inflation.
  46.                 mConstructorArgs[0] = mContext;
  47.             }
  48.             Object[] args = mConstructorArgs;
  49.             args[1] = attrs;
  50.             // 注释 1
  51.             final View view = constructor.newInstance(args);
  52.             if (view instanceof ViewStub) {
  53.                 // Use the same context when inflating ViewStub later.
  54.                 final ViewStub viewStub = (ViewStub) view;
  55.                 viewStub.setLayoutInflater(cloneInContext((Context) args[0]));
  56.             }
  57.             mConstructorArgs[0] = lastContext;
  58.             return view;
  59.         } catch (NoSuchMethodException e) {
  60.             final InflateException IE = new InflateException(attrs.getPositionDescription()
  61.                     + ": Error inflating class" + (prefix != null ? (prefix + name) : name), e);
  62.             IE.setStackTrace(EMPTY_STACK_TRACE);
  63.             throw IE;
  64.         } catch (ClassCastException e) {
  65.             // If loaded class is not a View subclass
  66.             final InflateException IE = new InflateException(attrs.getPositionDescription()
  67.                     + ": Class is not a View" + (prefix != null ? (prefix + name) : name), e);
  68.             IE.setStackTrace(EMPTY_STACK_TRACE);
  69.             throw IE;
  70.         } catch (ClassNotFoundException e) {
  71.             // If loadClass fails, we should propagate the exception.
  72.             throw e;
  73.         } catch (Exception e) {
  74.             final InflateException IE = new InflateException(
  75.                     attrs.getPositionDescription() + ": Error inflating class"
  76.                             + (clazz == null ? "<unknown>" : clazz.getName()), e);
  77.             IE.setStackTrace(EMPTY_STACK_TRACE);
  78.             throw IE;
  79.         } finally {
  80.             Trace.traceEnd(Trace.TRACE_TAG_VIEW);
  81.         }
  82.     }

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:

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <resources>
  3.     <declare-styleable name="Skin">
  4.         <attr name="skinChange" format="boolean" />
  5.     </declare-styleable>
  6. </resources>

skinChange 用于判断 View 是否需要进行换肤. 编写我们的布局文件:

  1. <?xml version="1.0" encoding="utf-8"?>
  2. <LinearLayout xmlns:Android="http://schemas.android.com/apk/res/android"
  3.     xmlns:App="http://schemas.android.com/apk/res-auto"
  4.     xmlns:tools="http://schemas.android.com/tools"
  5.     Android:layout_width="match_parent"
  6.     Android:layout_height="match_parent"
  7.     App:skinChange="true"
  8.     Android:background="@drawable/girl"
  9.     Android:orientation="vertical">
  10.     <Button
  11.         Android:id="@+id/btn_skin"
  12.         Android:layout_width="match_parent"
  13.         Android:layout_height="wrap_content"
  14.         Android:background="@color/text_color"
  15.         App:skinChange="true"
  16.         Android:text="点击进行换肤"
  17.         tools:ignore="MissingPrefix" />
  18.     <TextView
  19.         Android:layout_width="match_parent"
  20.         Android:layout_height="wrap_content"
  21.         App:skinChange="true"
  22.         Android:textSize="15sp"
  23.         Android:textColor="@color/text_color"
  24.         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"
  25.         tools:ignore="MissingPrefix" />
  26.     <ImageView
  27.         Android:layout_width="100dp"
  28.         Android:layout_height="100dp"
  29.         App:skinChange="true"
  30.         Android:src="@drawable/level"
  31.         Android:layout_marginTop="10dp"
  32.         tools:ignore="MissingPrefix" />
  33. </LinearLayout>

新建 SkinFactory 类并实现自 LayoutInflater.Factory2 接口:

  1. public class SkinFactory implements LayoutInflater.Factory2 {
  2.   public class SkinFactory implements LayoutInflater.Factory2 {
  3.     private AppCompatDelegate mDelegate;
  4.     static final Class<?>[] mConstructorSignature = new Class[]{Context.class, AttributeSet.class};//
  5.     final Object[] mConstructorArgs = new Object[2];
  6.     private static final HashMap<String, Constructor<? extends View>> sConstructorMap = new HashMap<String, Constructor<? extends View>>();
  7.     static final String[] prefix = new String[]{
  8.             "android.widget.",
  9.             "android.view.",
  10.             "android.webkit."
  11.     };
  12.     public void setDelegate(AppCompatDelegate delegate) {
  13.         this.mDelegate = delegate;
  14.     }
  15.     @Override
  16.     public View onCreateView(String name, Context context, AttributeSet attrs) {
  17.         return null;
  18.     }
  19.     @Override
  20.     public View onCreateView(View parent, String name, Context context, AttributeSet attrs) {
  21.         View view = mDelegate.createView(parent, name, context, attrs);
  22.         if (view == null) {
  23.             mConstructorArgs[0] = context;
  24.             try {
  25.                 if (-1 == name.indexOf('.')) {
  26.                     view = createViewByPrefix(context, name, prefix, attrs);
  27.                 } else {
  28.                     view = createViewByPrefix(context, name, null, attrs);
  29.                 }
  30.             } catch (Exception e) {
  31.                 e.printStackTrace();
  32.             }
  33.         }
  34.         // 保存需要换肤的 View
  35.         SkinChange.getInstance().saveSkin(context, attrs, view);
  36.         return view;
  37.     }
  38.     private  View createViewByPrefix(Context context, String name, String[] prefixs, AttributeSet attrs) {
  39.         Constructor<? extends View> constructor = sConstructorMap.get(name);
  40.         Class<? extends View> clazz = null;
  41.         if (constructor == null) {
  42.             try {
  43.                 if (prefixs != null && prefixs.length> 0) {
  44.                     for (String prefix : prefixs) {
  45.                         clazz = context.getClassLoader().loadClass(
  46.                                 prefix != null ? (prefix + name) : name).asSubclass(View.class);
  47.                         if (clazz != null) break;
  48.                     }
  49.                 } else {
  50.                     clazz = context.getClassLoader().loadClass(name).asSubclass(View.class);
  51.                 }
  52.                 if (clazz == null) {
  53.                     return null;
  54.                 }
  55.                 constructor = clazz.getConstructor(mConstructorSignature);
  56.             } catch (Exception e) {
  57.                 e.printStackTrace();
  58.                 return null;
  59.             }
  60.             constructor.setAccessible(true);
  61.             // 缓存
  62.             sConstructorMap.put(name, constructor);
  63.         }
  64.         Object[] args = mConstructorArgs;
  65.         args[1] = attrs;
  66.         try {
  67.             // 通过反射创建 View 对象
  68.             return constructor.newInstance(args);
  69.         } catch (Exception e) {
  70.             e.printStackTrace();
  71.         }
  72.         return null;
  73.     }
  74. }

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:

  1. public class SkinChange {
  2.     private SkinChange(){}
  3.     public static SkinChange getInstance(){
  4.         return Holder.SKIN_CHANGE;
  5.     }
  6.      private static class Holder{
  7.          private static final SkinChange SKIN_CHANGE=new SkinChange();
  8.     }
  9.     private List<SkinChange.Skin> mSkinListView = new ArrayList<>();
  10.     public List<SkinChange.Skin> getSkinViewList(){
  11.         return mSkinListView;
  12.     }
  13.     public void saveSkin(Context context, AttributeSet attrs, View view) {
  14.         TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.Skin);
  15.         boolean skin = a.getBoolean(R.styleable.Skin_skinChange, false);
  16.         if (skin) {
  17.             final int Len = attrs.getAttributeCount();
  18.             HashMap<String, String> attrMap = new HashMap<>();
  19.             for (int i = 0; i <Len; i++) {
  20.                 String attrName = attrs.getAttributeName(i);
  21.                 String attrValue = attrs.getAttributeValue(i);
  22.                 attrMap.put(attrName, attrValue);
  23.                 Log.d("saveSkin","attrName="+attrName+"attrValue="+attrValue);
  24.             }
  25.             SkinChange.Skin skinView = new SkinChange.Skin();
  26.             skinView.view = view;
  27.             skinView.attrsMap = attrMap;
  28.             mSkinListView.add(skinView);
  29.         }
  30.     }
  31.     public static class Skin{
  32.         View view;
  33.         HashMap<String, String> attrsMap;
  34.     }
  35. }

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:

  1. public abstract class BaseActivity extends AppCompatActivity {
  2.     private SkinFactory mSkinFactory;
  3.     @Override
  4.     protected void onCreate(@Nullable Bundle savedInstanceState) {
  5.         if(null == mSkinFactory){
  6.             mSkinFactory=new SkinFactory();
  7.         }
  8.         mSkinFactory.setDelegate(getDelegate());
  9.         LayoutInflater layoutInflater=LayoutInflater.from(this);
  10.         layoutInflater.setFactory2(mSkinFactory);
  11.         super.onCreate(savedInstanceState);
  12.     }
  13. }

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:

  1. public class LoadResources {
  2.     private Resources mSkinResources;
  3.     private Context mContext;
  4.     private String mOutPkgName;
  5.     public static LoadResources getInstance() {
  6.         return Holder.LOAD_RESOURCES;
  7.     }
  8.     private LoadResources() {
  9.     }
  10.     private static class Holder{
  11.         private static final LoadResources LOAD_RESOURCES=new LoadResources();
  12.     }
  13.     public void init(Context context) {
  14.         mContext = context.getApplicationContext();
  15.     }
  16.     public void load(final String path) {
  17.         File file = new File(path);
  18.         if (!file.exists()) {
  19.             return;
  20.         }
  21.         PackageManager mPm = mContext.getPackageManager();
  22.         PackageInfo mInfo = mPm.getPackageArchiveInfo(path, PackageManager.GET_ACTIVITIES);
  23.         mOutPkgName = mInfo.packageName;
  24.         AssetManager assetManager;
  25.         try {
  26.             assetManager = AssetManager.class.newInstance();
  27.             Method addAssetPath = assetManager.getClass().getMethod("addAssetPath", String.class);
  28.             addAssetPath.invoke(assetManager, path);
  29.             mSkinResources = new Resources(assetManager,
  30.                     mContext.getResources().getDisplayMetrics(),
  31.                     mContext.getResources().getConfiguration());
  32.         } catch (Exception e) {
  33.             e.printStackTrace();
  34.         }
  35.     }
  36.     public int getColor(int resId) {
  37.         if (mSkinResources == null) {
  38.             return resId;
  39.         }
  40.         String resName = mSkinResources.getResourceEntryName(resId);
  41.         int outResId = mSkinResources.getIdentifier(resName, "color", mOutPkgName);
  42.         if (outResId == 0) {
  43.             return resId;
  44.         }
  45.         return mSkinResources.getColor(outResId);
  46.     }
  47.     public Drawable getDrawable(int resId) {
  48.         if (mSkinResources == null) {
  49.             return ContextCompat.getDrawable(mContext, resId);
  50.         }
  51.         String resName = mSkinResources.getResourceEntryName(resId);
  52.         int outResId = mSkinResources.getIdentifier(resName, "drawable", mOutPkgName);
  53.         if (outResId == 0) {
  54.             return ContextCompat.getDrawable(mContext, resId);
  55.         }
  56.         return mSkinResources.getDrawable(outResId);
  57.     }
  58. }

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:

  1. public interface ISkinView {
  2.     void change(String path);
  3. }

创建 SkinChangeBiz 并实现 ISkinView 接口:

  1. public class SkinChangeBiz implements ISkinView {
  2.     private static class Holder {
  3.         private static final ISkinView SKIN_CHANGE_BIZ = new SkinChangeBiz();
  4.     }
  5.     public static ISkinView getInstance() {
  6.         return Holder.SKIN_CHANGE_BIZ;
  7.     }
  8.     @Override
  9.     public void change(String path) {
  10.         File skinFile = new File(Environment.getExternalStorageDirectory(), path);
  11.         LoadResources.getInstance().load(skinFile.getAbsolutePath());
  12.         for (SkinChange.Skin skinView : SkinChange.getInstance().getSkinViewList()) {
  13.             changeSkin(skinView);
  14.         }
  15.     }
  16.     void changeSkin(SkinChange.Skin skinView) {
  17.         if (!TextUtils.isEmpty(skinView.attrsMap.get("background"))) {
  18.             int bgId = Integer.parseInt(skinView.attrsMap.get("background").substring(1));
  19.             String attrType = skinView.view.getResources().getResourceTypeName(bgId);
  20.             if (TextUtils.equals(attrType, "drawable")) {
  21.                 skinView.view.setBackgroundDrawable(LoadResources.getInstance().getDrawable(bgId));
  22.             } else if (TextUtils.equals(attrType, "color")) {
  23.                 skinView.view.setBackgroundColor(LoadResources.getInstance().getColor(bgId));
  24.             }
  25.         }
  26.         if (skinView.view instanceof TextView) {
  27.             if (!TextUtils.isEmpty(skinView.attrsMap.get("textColor"))) {
  28.                 int textColorId = Integer.parseInt(skinView.attrsMap.get("textColor").substring(1));
  29.                 ((TextView) skinView.view).setTextColor(LoadResources.getInstance().getColor(textColorId));
  30.             }
  31.         }
  32.     }
  33. }

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.

  1. mBtnSkin.setOnClickListener(new View.OnClickListener() {
  2.             @Override
  3.             public void onClick(View v) {
  4.                 // 进行换肤
  5.                 SkinChangeBiz.getInstance().change("skinPlugin.apk");
  6.             }
  7.         });

运行效果如下:

GitHub 地址请点击这里 https://github.com/LinhaiGu/SkinProject

来源: https://juejin.im/post/5c6d20f4f265da2da00eaa44


与本文相关文章

  1. 技术高手如何炼成
  2. 关于图文识别功能相关技术的大致实现
  3. 异步编程相关技术实现
  4. 2016 中国大数据技术大会 相关资料
  5. 如何学习后端技术?
  6. 腾讯 AI Lab 深度解读文本生成技术相关论文
  7. 如何正确使用缓存技术
  8. MySQL 复制相关技术初步小结
暂无,快来抢沙发吧！
更多





黑ICP备17005318号-1