android自定義屬性，解決xml泛濫問題

author:andy

  • 日常定義Button最常用的就是使用 xml中定義好,然后加上backgroud屬性，然后部分特殊效果，單獨加上xml文件的背景效果，比如：
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <solid android:color="@color/color_white" />
    <corners android:radius="12dp" />
</shape>

問題1

當今天設計給個5dp，明天設計給個8dp，后天上面需要2個角為5dp，我們的xml定義的drawable,將會無限膨脹，越來越多。。。。

問題2

市面上換膚框架的基礎原理，是啥？

為了解決這個問題1，我們就需要分2步：
1.從 xml加載成Button,
2.xml加載成drawable的圖片背景，然后再用Button設置圖片背景 的流程

步驟1:xml控件加載流程圖

xml加載圖.png

根據(jù)xml加載控件流程圖，factory2加載xml優(yōu)先，如果我們自己定義factory2，就可以攔截整個View生成的流程：

class MainActivity : AppCompatActivity() {
    companion object {
        const val TAG = "MainActivity"
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        LayoutInflater.from(this).factory2 = object : LayoutInflater.Factory2 {
            override fun onCreateView(
                parent: View?,
                name: String,
                context: Context,
                attrs: AttributeSet
            ): View? {
                Log.i(TAG, "name=$name ")
                val view = this@MainActivity.delegate.createView(parent, name, context, attrs)
                val typeArray =
                    context.obtainStyledAttributes(attrs, R.styleable.CustomeDrawable)
                for (i in 0 until attrs.attributeCount) {
                    Log.i(
                        TAG,
                        " name ${attrs.getAttributeName(i)}   value=${attrs.getAttributeValue(i)}"
                    )
                }
                val radius =
                    typeArray.getDimension(R.styleable.CustomeDrawable_corner_radius, 0f)
                if (radius > 0) {
                    val drawable = GradientDrawable()
                    drawable.cornerRadius = radius
                    drawable.setColor((Color.parseColor("#ff0000")))
                    view?.background = drawable
                }
                typeArray.recycle()
                return view
            }

            override fun onCreateView(name: String, context: Context, attrs: AttributeSet): View? {
                return null;
            }

        }
        setContentView(R.layout.activity_main)
        btn_join?.setOnClickListener {
            startActivity(Intent(baseContext, TwoActivity::class.java))
        }
    }
}

然而問題是會報

   Caused by: java.lang.IllegalStateException: A factory has already been set on this LayoutInflater
        at android.view.LayoutInflater.setFactory2(LayoutInflater.java:369)
        at com.yy.customedrawable.MainActivity.onCreate(MainActivity.kt:22)
        at android.app.Activity.performCreate(Activity.java:7966)
        at android.app.Activity.performCreate(Activity.java:7955)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1306)

再次看源碼AppCompatActivity的oncreate()方法

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        final AppCompatDelegate delegate = getDelegate();
        delegate.installViewFactory();
        delegate.onCreate(savedInstanceState);
        super.onCreate(savedInstanceState);
    }

AppCompatDelegateImpl中的 installViewFactory

    @Override
    public void installViewFactory() {
        LayoutInflater layoutInflater = LayoutInflater.from(mContext);
        if (layoutInflater.getFactory() == null) {
            LayoutInflaterCompat.setFactory2(layoutInflater, this);
        } else {
            if (!(layoutInflater.getFactory2() instanceof AppCompatDelegateImpl)) {
                Log.i(TAG, "The Activity's LayoutInflater already has a Factory installed"
                        + " so we can not install AppCompat's");
            }
        }
    }

根據(jù)源碼，AppCompatActivity--oncreate（）已經(jīng)會自己創(chuàng)建factory2，所以只需要設置我們的factory2，在super.oncreate(),之前即可

然而AppCompatActiivty設置factory2就是為了兼容新定義的AppCompatTextView,AppCompatButton等等，所以我們?yōu)榱思嫒葜荒苓@么處理

 val view = this@MainActivity.delegate.createView(parent, name, context, attrs)

步驟2:

xml加載為圖片背景 (xml->drawable流程)


xml加載背景流程圖.png

DrawableInflater.inflaterFromTag()

 private Drawable inflateFromTag(@NonNull String name) {
        switch (name) {
            case "selector":
                return new StateListDrawable();
            case "animated-selector":
                return new AnimatedStateListDrawable();
            case "level-list":
                return new LevelListDrawable();
            case "layer-list":
                return new LayerDrawable();
            case "transition":
                return new TransitionDrawable();
            case "ripple":
                return new RippleDrawable();
            case "adaptive-icon":
                return new AdaptiveIconDrawable();
            case "color":
                return new ColorDrawable();
            case "shape":
                return new GradientDrawable();
            case "vector":
                return new VectorDrawable();
            case "animated-vector":
                return new AnimatedVectorDrawable();
            case "scale":
                return new ScaleDrawable();
            case "clip":
                return new ClipDrawable();
            case "rotate":
                return new RotateDrawable();
            case "animated-rotate":
                return new AnimatedRotateDrawable();
            case "animation-list":
                return new AnimationDrawable();
            case "inset":
                return new InsetDrawable();
            case "bitmap":
                return new BitmapDrawable();
            case "nine-patch":
                return new NinePatchDrawable();
            case "animated-image":
                return new AnimatedImageDrawable();
            default:
                return null;
        }
    }

根據(jù)上面2個圖，可以看出最終我們的xml最終轉換成了一個個對象(StateListDrawable,ColorDrawable等),也就是說我們只需要將xml定義的屬性轉化成 Drawable 的子類就可以。

如何自定義相關屬性，減少xml的定義

  • 方法1 既然xml圖片背景最終生成drawable,完全可以使用drawable的子類，然后自己設置
    上代碼
       //方式1
        TextView tv = findViewById(R.id.test_view1);
        tv.setClickable(true);
        ColorStateList colors = new DrawableCreator.Builder().setPressedTextColor(Color.RED
        ).setUnPressedTextColor(Color.BLUE).buildTextColor();
        tv.setTextColor(colors);
  • 方法2 注冊factory2，xml直接使用自定義屬性
    注意：由于自定義的 xml屬性，androidstudio 不支持，所以會報紅，只能加上
    tools:ignore="MissingPrefix" 屬性避免了
    <Button
        android:id="@+id/btn_feedback"
        app:layout_constraintStart_toStartOf="@id/top_view"
        app:layout_constraintEnd_toEndOf="@id/top_view"
        app:layout_constraintTop_toBottomOf="@id/test_view1"
        android:layout_width="300dp"
        android:layout_height="50dp"
        android:layout_marginTop="15dp"
        android:gravity="center"
        android:padding="0dp"
        android:text="方式2-factory"
        android:textColor="@android:color/white"
        android:textSize="20sp"
        app:bl_corners_radius="20dp"
        app:bl_pressed_color="#7CCD7C"
        app:bl_shape="rectangle"
        app:bl_unpressed_color="#7CFC00" />

在activity中注冊factory2

  public static LayoutInflater inject(Context context) {
        LayoutInflater inflater;
        if (context instanceof Activity) {
            inflater = ((Activity) context).getLayoutInflater();
        } else {
            inflater = LayoutInflater.from(context);
        }
        if (inflater == null) {
            return null;
        }
        if (inflater.getFactory2() == null) {
            BackgroundFactory factory = setDelegateFactory(context);
            inflater.setFactory2(factory);
        } else if (!(inflater.getFactory2() instanceof BackgroundFactory)) {
            forceSetFactory2(inflater);
        }
        return inflater;
    }

如果activity繼承AppCompatActivity就使用系統(tǒng)的factory2

    @NonNull
    private static BackgroundFactory setDelegateFactory(Context context) {
        BackgroundFactory factory = new BackgroundFactory();
        if (context instanceof AppCompatActivity) {
            final AppCompatDelegate delegate = ((AppCompatActivity) context).getDelegate();
            factory.setInterceptFactory(new LayoutInflater.Factory() {
                @Override
                public View onCreateView(String name, Context context, AttributeSet attrs) {
                    return delegate.createView(null, name, context, attrs);
                }
            });
        }
        return factory;
    }

如果已經(jīng)設置過factory2，那么反射修改factory2為自己的 BackgroundFactory

  private static void forceSetFactory2(LayoutInflater inflater) {
        Class<LayoutInflaterCompat> compatClass = LayoutInflaterCompat.class;
        Class<LayoutInflater> inflaterClass = LayoutInflater.class;
        try {
            Field sCheckedField = compatClass.getDeclaredField("sCheckedField");
            sCheckedField.setAccessible(true);
            sCheckedField.setBoolean(inflater, false);
            Field mFactory = inflaterClass.getDeclaredField("mFactory");
            mFactory.setAccessible(true);
            Field mFactory2 = inflaterClass.getDeclaredField("mFactory2");
            mFactory2.setAccessible(true);
            BackgroundFactory factory = new BackgroundFactory();
            if (inflater.getFactory2() != null) {
                factory.setInterceptFactory2(inflater.getFactory2());
            } else if (inflater.getFactory() != null) {
                factory.setInterceptFactory(inflater.getFactory());
            }
            mFactory2.set(inflater, factory);
            mFactory.set(inflater, factory);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (NoSuchFieldException e) {
            e.printStackTrace();
        }
    }
  • 方法3定義view繼承 系統(tǒng)的控件,利用自帶的factory2，生成view，再解析自定義的atrribute，解析，然后設置相關屬性背景等。。。
public class BLTextView extends AppCompatTextView {
    public BLTextView(Context context) {
        super(context);
    }

    public BLTextView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context, attrs);
    }

    public BLTextView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context, attrs);
    }

    private void init(Context context, AttributeSet attrs) {
        BackgroundFactory.setViewBackground(context, attrs, this);
    }
}

xml中的調用

    <com.noober.background.view.BLTextView
        android:id="@+id/bl_text_view"
        android:layout_width="120dp"
        android:layout_height="48dp"
        android:text="方式3-textview"
        android:gravity="center"
        app:layout_constraintStart_toStartOf="@id/top_view"
        app:layout_constraintEnd_toEndOf="@id/top_view"
        app:layout_constraintTop_toBottomOf="@id/btn_feedback"
        android:layout_marginTop="20dp"
        app:bl_pressed_drawable="#9DD1F6"
        app:bl_unPressed_drawable="#1B82D1"
        />

-： 最新的androidstudio，已經(jīng)支持自定義的屬性直接顯示了，簡直666
上一個demo[]

資源加載應用----換膚原理-流程(1.獲取attributeSet屬性 2.加載資源和替換)

  ContextImpl appContext = ContextImpl.createAppContext(mActivityThread, this);
->ContextImpl context = new ContextImpl(
->  context.setResources(packageInfo.getResources());
->  mResources = ResourcesManager.getInstance().getResources(。。
-> return getOrCreateResources(activityToken, key, classLoader);
->如果已經(jīng)緩存就 ResourcesImpl resourcesImpl = findResourcesImplForKeyLocked(key);
->ResourcesImpl resourcesImpl = createResourcesImpl(key);
-> final AssetManager assets = createAssetManager(key);
->assets.addAssetPath(key.mResDir)  
該方法內(nèi)調用native方法完成資源加載

---換膚的核心的資源的替換
--AssetManager.addAssetPath() -> addAssetPathInternal(String path, boolean appAsLib)
將資源庫apk加載到assetManager

 /**
     * 記載皮膚并應用
     *
     * @param skinPath 皮膚路徑 如果為空則使用默認皮膚
     */
    public void loadSkin(String skinPath) {
        if (TextUtils.isEmpty(skinPath)) {
            //還原默認皮膚
            SkinPreference.getInstance().reset();
            SkinResources.getInstance().reset();
        } else {
            try {
                //宿主app的 resources;
                Resources appResource = mContext.getResources();
//
                //反射創(chuàng)建AssetManager 與 Resource
                AssetManager assetManager = AssetManager.class.newInstance();
                //資源路徑設置 目錄或壓縮包
                Method addAssetPath = assetManager.getClass().getMethod("addAssetPath",
                        String.class);
                addAssetPath.invoke(assetManager, skinPath);

                //根據(jù)當前的設備顯示器信息 與 配置(橫豎屏、語言等) 創(chuàng)建Resources
                Resources skinResource = new Resources(assetManager, appResource.getDisplayMetrics
                        (), appResource.getConfiguration());

                //獲取外部Apk(皮膚包) 包名
                PackageManager mPm = mContext.getPackageManager();
                PackageInfo info = mPm.getPackageArchiveInfo(skinPath, PackageManager
                        .GET_ACTIVITIES);
                String packageName = info.packageName;
                SkinResources.getInstance().applySkin(skinResource, packageName);

                //記錄
                SkinPreference.getInstance().setSkin(skinPath);


            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        //通知采集的View 更新皮膚
        //被觀察者改變 通知所有觀察者
        setChanged();
        notifyObservers(null);
    }
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