Android屏幕適配-第三篇（今日頭條適配方案）

今天記錄的筆記是今日頭條的適配方案原理以及開源庫”AndroidAutoSize“的實現剖析！（備註：此文僅供自己參考，全文全是文字，如果讀者讀起來比較生澀難懂，建議閱讀引入文章）

此篇文章是通過閱讀《騷年你的屏幕適配方式該升級了!-今日頭條適配方案》理解的整理。感謝作者JessYan

適配的前提是你需要知道安卓適配的基礎知識和基本方法 《Android屏幕適配-第一篇（基礎知識）》、《Android屏幕適配-第二篇（你要知道的適配基本操作）》

你需要知道的關鍵字：density、dip、px、dp(dpi)

今日頭條適配原理：density=（當前屏幕分辨率寬或高(單位px)）/(ui設計稿寬或高(單位dp))

                                 這個表示的是1dp在當前分辨率下的所對於的像素

真正的view大小： realWidth=(ui設計稿上的寬度)*density

如何使用，例子：如設置一個view大小爲100dpx100dp，通過上面的公式可得到寬爲100*density高爲100*density

                            假設當前分辨率爲720x1280,設計搞的尺寸爲360x640,當前density=2

                            假設當前分辨率爲480x800,設計搞的尺寸爲360x640,當前density=1.333

                            分辨率爲720x1280下 view寬度=100*2 px,佔整體寬度的比例爲0.278（約等於）

                            分辨率爲480x800下 view寬度=100*1.33 px,佔整體寬度的比例爲0.278(約等於)

                            比例近乎相同             

AndroidAutoSize分析      

 設置設計稿 寬或高 

        <!-- 如果您項目中的所有頁面都只需要以高或寬中的一個作爲基準進行適配的話, 那就只需要填寫高或寬中的一個設計圖尺寸即可 -->
        <meta-data
            android:name="design_width_in_dp"
            android:value="360"/>
        <meta-data
            android:name="design_height_in_dp"
            android:value="640"/>

 初始化配置，通過啓動一個ContenProvider來啓動默認配置

/**
 * ================================================
 * 通過聲明 {@link ContentProvider} 自動完成初始化
 * Created by JessYan on 2018/8/19 11:55
 * <a href="mailto:[email protected]">Contact me</a>
 * <a href="https://github.com/JessYanCoding">Follow me</a>
 * ================================================
 */
public class InitProvider extends ContentProvider {
    @Override
    public boolean onCreate() {
        AutoSizeConfig.getInstance()
                .setLog(true)
                .init((Application) getContext().getApplicationContext())
                .setUseDeviceSize(false);
        return true;
    }
    //其他代碼忽略...
}

然後會調用此方法

    AutoSizeConfig init(final Application application, boolean isBaseOnWidth, AutoAdaptStrategy strategy) {
        Preconditions.checkArgument(mInitDensity == -1, "AutoSizeConfig#init() can only be called once");
        Preconditions.checkNotNull(application, "application == null");
        this.mApplication = application;
        this.isBaseOnWidth = isBaseOnWidth;
        final DisplayMetrics displayMetrics = Resources.getSystem().getDisplayMetrics();

        getMetaData(application);
        isVertical = application.getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT;
        int[] screenSize = ScreenUtils.getScreenSize(application);
        mScreenWidth = screenSize[0];
        mScreenHeight = screenSize[1];
        mStatusBarHeight = ScreenUtils.getStatusBarHeight();
        LogUtils.d("designWidthInDp = " + mDesignWidthInDp + ", designHeightInDp = " + mDesignHeightInDp + ", screenWidth = " + mScreenWidth + ", screenHeight = " + mScreenHeight);

        mInitDensity = displayMetrics.density;
        mInitDensityDpi = displayMetrics.densityDpi;
        mInitScaledDensity = displayMetrics.scaledDensity;
        mInitXdpi = displayMetrics.xdpi;
        application.registerComponentCallbacks(new ComponentCallbacks() {
            @Override
            public void onConfigurationChanged(Configuration newConfig) {
                if (newConfig != null) {
                    if (newConfig.fontScale > 0) {
                        mInitScaledDensity =
                                Resources.getSystem().getDisplayMetrics().scaledDensity;
                        LogUtils.d("initScaledDensity = " + mInitScaledDensity + " on ConfigurationChanged");
                    }
                    isVertical = newConfig.orientation == Configuration.ORIENTATION_PORTRAIT;
                    int[] screenSize = ScreenUtils.getScreenSize(application);
                    mScreenWidth = screenSize[0];
                    mScreenHeight = screenSize[1];
                }
            }

            @Override
            public void onLowMemory() {

            }
        });
        ....
        //注意看這句代碼是        
        mActivityLifecycleCallbacks = new ActivityLifecycleCallbacksImpl(strategy == null ? new WrapperAutoAdaptStrategy(new DefaultAutoAdaptStrategy()) : strategy);
        application.registerActivityLifecycleCallbacks(mActivityLifecycleCallbacks);
        ....
        return this;
    }

  ActivityLifecycleCallbacksImpl這裏面有很多核心代碼

/**
 * ================================================
 * {@link ActivityLifecycleCallbacksImpl} 可用來代替在 BaseActivity 中加入適配代碼的傳統方式
 * {@link ActivityLifecycleCallbacksImpl} 這種方案類似於 AOP, 面向接口, 侵入性低, 方便統一管理, 擴展性強, 並且也支持適配三方庫的 {@link Activity}
 * <p>
 * Created by JessYan on 2018/8/8 14:32
 * <a href="mailto:[email protected]">Contact me</a>
 * <a href="https://github.com/JessYanCoding">Follow me</a>
 * ================================================
 */
public class ActivityLifecycleCallbacksImpl implements Application.ActivityLifecycleCallbacks {
    /**
     * 屏幕適配邏輯策略類
     */
    private AutoAdaptStrategy mAutoAdaptStrategy;
    /**
     * 讓 {@link Fragment} 支持自定義適配參數
     */
    private FragmentLifecycleCallbacksImpl mFragmentLifecycleCallbacks;

    public ActivityLifecycleCallbacksImpl(AutoAdaptStrategy autoAdaptStrategy) {
        mFragmentLifecycleCallbacks = new FragmentLifecycleCallbacksImpl(autoAdaptStrategy);
        mAutoAdaptStrategy = autoAdaptStrategy;
    }

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
        if (AutoSizeConfig.getInstance().isCustomFragment()) {
            if (activity instanceof FragmentActivity) {
                ((FragmentActivity) activity).getSupportFragmentManager().registerFragmentLifecycleCallbacks(mFragmentLifecycleCallbacks, true);
            }
        }

        //Activity 中的 setContentView(View) 一定要在 super.onCreate(Bundle); 之後執行
        if (mAutoAdaptStrategy != null) {
            mAutoAdaptStrategy.applyAdapt(activity, activity);
        }
    }

    @Override
    public void onActivityStarted(Activity activity) {
        if (mAutoAdaptStrategy != null) {
            mAutoAdaptStrategy.applyAdapt(activity, activity);
        }
    }

    ...

    /**
     * 設置屏幕適配邏輯策略類
     *
     * @param autoAdaptStrategy {@link AutoAdaptStrategy}
     */
    public void setAutoAdaptStrategy(AutoAdaptStrategy autoAdaptStrategy) {
        mAutoAdaptStrategy = autoAdaptStrategy;
        mFragmentLifecycleCallbacks.setAutoAdaptStrategy(autoAdaptStrategy);
    }
}

 DefaultAutoAdaptStrategy裏面幹了什麼事情

/**
 * ================================================
 * 屏幕適配邏輯策略默認實現類, 可通過 {@link AutoSizeConfig#init(Application, boolean, AutoAdaptStrategy)}
 * 和 {@link AutoSizeConfig#setAutoAdaptStrategy(AutoAdaptStrategy)} 切換策略
 *
 * @see AutoAdaptStrategy
 * Created by JessYan on 2018/8/9 15:57
 * <a href="mailto:[email protected]">Contact me</a>
 * <a href="https://github.com/JessYanCoding">Follow me</a>
 * ================================================
 */
public class DefaultAutoAdaptStrategy implements AutoAdaptStrategy {
    @Override
    public void applyAdapt(Object target, Activity activity) {

        //檢查是否開啓了外部三方庫的適配模式, 只要不主動調用 ExternalAdaptManager 的方法, 下面的代碼就不會執行
        if (AutoSizeConfig.getInstance().getExternalAdaptManager().isRun()) {
            if (AutoSizeConfig.getInstance().getExternalAdaptManager().isCancelAdapt(target.getClass())) {
                LogUtils.w(String.format(Locale.ENGLISH, "%s canceled the adaptation!", target.getClass().getName()));
                AutoSize.cancelAdapt(activity);
                return;
            } else {
                ExternalAdaptInfo info = AutoSizeConfig.getInstance().getExternalAdaptManager()
                        .getExternalAdaptInfoOfActivity(target.getClass());
                if (info != null) {
                    LogUtils.d(String.format(Locale.ENGLISH, "%s used %s for adaptation!", target.getClass().getName(), ExternalAdaptInfo.class.getName()));
                    AutoSize.autoConvertDensityOfExternalAdaptInfo(activity, info);
                    return;
                }
            }
        }

        //如果 target 實現 CancelAdapt 接口表示放棄適配, 所有的適配效果都將失效
        if (target instanceof CancelAdapt) {
            LogUtils.w(String.format(Locale.ENGLISH, "%s canceled the adaptation!", target.getClass().getName()));
            AutoSize.cancelAdapt(activity);
            return;
        }

        //如果 target 實現 CustomAdapt 接口表示該 target 想自定義一些用於適配的參數, 從而改變最終的適配效果
        if (target instanceof CustomAdapt) {
            LogUtils.d(String.format(Locale.ENGLISH, "%s implemented by %s!", target.getClass().getName(), CustomAdapt.class.getName()));
            AutoSize.autoConvertDensityOfCustomAdapt(activity, (CustomAdapt) target);
        } else {
            LogUtils.d(String.format(Locale.ENGLISH, "%s used the global configuration.", target.getClass().getName()));
            AutoSize.autoConvertDensityOfGlobal(activity);
        }
    }
}

  AutoSize 

    public static void autoConvertDensityOfCustomAdapt(Activity activity, CustomAdapt customAdapt) {
        Preconditions.checkNotNull(customAdapt, "customAdapt == null");
        float sizeInDp = customAdapt.getSizeInDp();

        //如果 CustomAdapt#getSizeInDp() 返回 0, 則使用在 AndroidManifest 上填寫的設計圖尺寸
        if (sizeInDp <= 0) {
            if (customAdapt.isBaseOnWidth()) {
                sizeInDp = AutoSizeConfig.getInstance().getDesignWidthInDp();
            } else {
                sizeInDp = AutoSizeConfig.getInstance().getDesignHeightInDp();
            }
        }
        autoConvertDensity(activity, sizeInDp, customAdapt.isBaseOnWidth());
    }

       /**
     * 這裏是今日頭條適配方案的核心代碼, 核心在於根據當前設備的實際情況做自動計算並轉換 {@link DisplayMetrics#density}、
     * {@link DisplayMetrics#scaledDensity}、{@link DisplayMetrics#densityDpi} 這三個值, 額外增加 {@link DisplayMetrics#xdpi}
     * 以支持單位 {@code pt}、{@code in}、{@code mm}
     *
     * @param activity      {@link Activity}
     * @param sizeInDp      設計圖上的設計尺寸, 單位 dp, 如果 {@param isBaseOnWidth} 設置爲 {@code true},
     *                      {@param sizeInDp} 則應該填寫設計圖的總寬度, 如果 {@param isBaseOnWidth} 設置爲 {@code false},
     *                      {@param sizeInDp} 則應該填寫設計圖的總高度
     * @param isBaseOnWidth 是否按照寬度進行等比例適配, {@code true} 爲以寬度進行等比例適配, {@code false} 爲以高度進行等比例適配
     * @see <a href="https://mp.weixin.qq.com/s/d9QCoBP6kV9VSWvVldVVwA">今日頭條官方適配方案</a>
     */
    public static void autoConvertDensity(Activity activity, float sizeInDp, boolean isBaseOnWidth) {
        Preconditions.checkNotNull(activity, "activity == null");

        float subunitsDesignSize = isBaseOnWidth ? AutoSizeConfig.getInstance().getUnitsManager().getDesignWidth()
                : AutoSizeConfig.getInstance().getUnitsManager().getDesignHeight();
        subunitsDesignSize = subunitsDesignSize > 0 ? subunitsDesignSize : sizeInDp;

        int screenSize = isBaseOnWidth ? AutoSizeConfig.getInstance().getScreenWidth()
                : AutoSizeConfig.getInstance().getScreenHeight();
        String key = sizeInDp + "|" + subunitsDesignSize + "|" + isBaseOnWidth + "|"
                + AutoSizeConfig.getInstance().isUseDeviceSize() + "|"
                + AutoSizeConfig.getInstance().getInitScaledDensity() + "|"
                + screenSize;

        DisplayMetricsInfo displayMetricsInfo = mCache.get(key);

        float targetDensity = 0;
        int targetDensityDpi = 0;
        float targetScaledDensity = 0;
        float targetXdpi = 0;

        if (displayMetricsInfo == null) {
            if (isBaseOnWidth) {
                targetDensity = AutoSizeConfig.getInstance().getScreenWidth() * 1.0f / sizeInDp;
            } else {
                targetDensity = AutoSizeConfig.getInstance().getScreenHeight() * 1.0f / sizeInDp;
            }
            float scale = AutoSizeConfig.getInstance().isExcludeFontScale() ? 1 : AutoSizeConfig.getInstance().
                    getInitScaledDensity() * 1.0f / AutoSizeConfig.getInstance().getInitDensity();
            targetScaledDensity = targetDensity * scale;
            targetDensityDpi = (int) (targetDensity * 160);

            if (isBaseOnWidth) {
                targetXdpi = AutoSizeConfig.getInstance().getScreenWidth() * 1.0f / subunitsDesignSize;
            } else {
                targetXdpi = AutoSizeConfig.getInstance().getScreenHeight() * 1.0f / subunitsDesignSize;
            }

            mCache.put(key, new DisplayMetricsInfo(targetDensity, targetDensityDpi, targetScaledDensity, targetXdpi));
        } else {
            targetDensity = displayMetricsInfo.getDensity();
            targetDensityDpi = displayMetricsInfo.getDensityDpi();
            targetScaledDensity = displayMetricsInfo.getScaledDensity();
            targetXdpi = displayMetricsInfo.getXdpi();
        }

        setDensity(activity, targetDensity, targetDensityDpi, targetScaledDensity, targetXdpi);

        LogUtils.d(String.format(Locale.ENGLISH, "The %s has been adapted! \n%s Info: isBaseOnWidth = %s, %s = %f, %s = %f, targetDensity = %f, targetScaledDensity = %f, targetDensityDpi = %d, targetXdpi = %f"
                , activity.getClass().getName(), activity.getClass().getSimpleName(), isBaseOnWidth, isBaseOnWidth ? "designWidthInDp"
                        : "designHeightInDp", sizeInDp, isBaseOnWidth ? "designWidthInSubunits" : "designHeightInSubunits", subunitsDesignSize
                , targetDensity, targetScaledDensity, targetDensityDpi, targetXdpi));
    }

 由此可見autoConvertDensity()方法是核心代碼

 這裏還匹配了pt in mm 爲單位的適配

    private static void setDensity(DisplayMetrics displayMetrics, float density, int densityDpi, float scaledDensity, float xdpi) {
        if (AutoSizeConfig.getInstance().getUnitsManager().isSupportDP()) {
            displayMetrics.density = density;
            displayMetrics.densityDpi = densityDpi;
        }
        if (AutoSizeConfig.getInstance().getUnitsManager().isSupportSP()) {
            displayMetrics.scaledDensity = scaledDensity;
        }
        switch (AutoSizeConfig.getInstance().getUnitsManager().getSupportSubunits()) {
            case NONE:
                break;
            case PT:
                displayMetrics.xdpi = xdpi * 72f;
                break;
            case IN:
                displayMetrics.xdpi = xdpi;
                break;
            case MM:
                displayMetrics.xdpi = xdpi * 25.4f;
                break;
            default:
        }
    }