最近要在App中添加夜間模式，一般來(lái)說(shuō)，夜間模式使用主題的方式實(shí)現(xiàn)，但因?yàn)锳pp中歷史遺留問(wèn)題較多，更換主題的方式工作量比較大，所以就打算在App的每一個(gè)Activity中添加一層半透明的黑色遮罩來(lái)實(shí)現(xiàn)。

開(kāi)啟夜間模式時(shí)，在每一個(gè)Activity的Window中添加一個(gè)半透明View，并把View保存起來(lái)，關(guān)閉夜間模式時(shí)從Window中移除這個(gè)View，核心代碼如下：

// 開(kāi)啟夜間模式
fun Activity.nightMode(): View {
    val nightViewParam = WindowManager.LayoutParams(
            WindowManager.LayoutParams.TYPE_APPLICATION,
            WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE or WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
                    /*or WindowManager.LayoutParams.FLAG_FULLSCREEN */ or WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS
                    or WindowManager.LayoutParams.FLAG_TRANSLUCENT_NAVIGATION,
            PixelFormat.TRANSPARENT)
    nightViewParam.width = ViewGroup.LayoutParams.MATCH_PARENT
    nightViewParam.height = ViewGroup.LayoutParams.MATCH_PARENT
    nightViewParam.gravity = Gravity.CENTER
    val nightView = View(this)
    nightView.setBackgroundColor(0x99000000.toInt())
    windowManager.addView(nightView, nightViewParam)
    return nightView
}

// 關(guān)閉夜間模式
fun Activity.removeNightMode(view: View?) = view?.let { windowManager.removeViewImmediate(view) }

要在每一個(gè)Activity中都去做一次判斷會(huì)比較繁瑣，一種方式是通過(guò)在基類(lèi)BaseActivity onStart中添加相關(guān)的代碼判斷當(dāng)前是否是夜間模式，另一種方式是我在之前的文章Android判斷程序回到前臺(tái)并獲取剪貼板數(shù)據(jù)中提到的在Application中注冊(cè)ActivityLifecycleCallbacks的方式來(lái)處理。

// Application中
private WeakHashMap<Activity, View> nightModeHashMap = new WeakHashMap<>();

registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
    }

    @Override
    public void onActivityStarted(Activity activity) {
        checkNightMode(activity);
    }

    @Override
    public void onActivityResumed(Activity activity) {
    }

    @Override
    public void onActivityPaused(Activity activity) {
    }

    @Override
    public void onActivityStopped(Activity activity) {
    }

    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
    }

    @Override
    public void onActivityDestroyed(Activity activity) {
        if (nightModeHashMap.containsKey(activity)) {
            nightModeHashMap.remove(activity);
        }
    }
});

public void checkNightMode(Activity activity) {
    if (activity == null) return;
    if (SharedPreferencesHelper.isNightMode()) {
        if (!nightModeHashMap.containsKey(activity))
            nightModeHashMap.put(activity, ActivityExtensionKt.nightMode(activity));
    } else {
        if (nightModeHashMap.containsKey(activity)) {
            ActivityExtensionKt.removeNightMode(activity, nightModeHashMap.get(activity));
            nightModeHashMap.remove(activity);
        }
    }
}

這種方式好處是不用修改Activity的代碼，可以覆蓋App中所有的頁(yè)面，甚至是第三方SDK中的頁(yè)面，并且后期要移除這個(gè)功能的時(shí)候也很容易。