官方链接：https://developer.chrome.com/multidevice/android/customtabs

image.png

1.

根据官方描述，Chrome Custom Tabs的速度比WebView快2倍左右，Chrome Custom Tabs其实是使用了默认浏览器来打开页面。相对于WebView而言，Chrome Custom Tabs无法通过js回调本地方法。所以一般来说如果要加载的网页是我们自己的（自己公司前端写的）就用WebView，如果加载的是外部网页，比如一个外部新闻链接，那么就用Chrome Custom Tabs

2.

一般来说在加载网页之前是需要判断的（从用户体验上来说，是用WebView还是Chrome Custom Tabs），即使要加载的是外部网页，因为默认的浏览器可能不是原生的。比如说用户下载了qq浏览器并将qq浏览器设置为了默认浏览器，这时候你再用Chrome Custom Tabs来打开会发现它启动了qq浏览器，很明显的启动效果（跟之前使用webView时不在app内加载是一样的效果，体验很差）

3.

判断
官方demo：https://github.com/GoogleChrome/custom-tabs-client
demo中的判断方法是在CustomTabsHelper类中

 /**
     * Goes through all apps that handle VIEW intents and have a warmup service. Picks
     * the one chosen by the user if there is one, otherwise makes a best effort to return a
     * valid package name.
     *
     * This is <strong>not</strong> threadsafe.
     *
     * @param context {@link Context} to use for accessing {@link PackageManager}.
     * @return The package name recommended to use for connecting to custom tabs related components.
     */
    public static String getPackageNameToUse(Context context) {
        if (sPackageNameToUse != null) return sPackageNameToUse;

        PackageManager pm = context.getPackageManager();
        // Get default VIEW intent handler.
        Intent activityIntent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.example.com"));
        ResolveInfo defaultViewHandlerInfo = pm.resolveActivity(activityIntent, 0);
        String defaultViewHandlerPackageName = null;
        if (defaultViewHandlerInfo != null) {
            defaultViewHandlerPackageName = defaultViewHandlerInfo.activityInfo.packageName;
        }

        // Get all apps that can handle VIEW intents.
        List<ResolveInfo> resolvedActivityList = pm.queryIntentActivities(activityIntent, 0);
        List<String> packagesSupportingCustomTabs = new ArrayList<>();
        for (ResolveInfo info : resolvedActivityList) {
            Intent serviceIntent = new Intent();
            serviceIntent.setAction(ACTION_CUSTOM_TABS_CONNECTION);
            serviceIntent.setPackage(info.activityInfo.packageName);
            if (pm.resolveService(serviceIntent, 0) != null) {
                packagesSupportingCustomTabs.add(info.activityInfo.packageName);
            }
        }

        // Now packagesSupportingCustomTabs contains all apps that can handle both VIEW intents
        // and service calls.
        if (packagesSupportingCustomTabs.isEmpty()) {
            sPackageNameToUse = null;
        } else if (packagesSupportingCustomTabs.size() == 1) {
            sPackageNameToUse = packagesSupportingCustomTabs.get(0);
        } else if (!TextUtils.isEmpty(defaultViewHandlerPackageName)
                && !hasSpecializedHandlerIntents(context, activityIntent)
                && packagesSupportingCustomTabs.contains(defaultViewHandlerPackageName)) {
            sPackageNameToUse = defaultViewHandlerPackageName;
        } else if (packagesSupportingCustomTabs.contains(STABLE_PACKAGE)) {
            sPackageNameToUse = STABLE_PACKAGE;
        } else if (packagesSupportingCustomTabs.contains(BETA_PACKAGE)) {
            sPackageNameToUse = BETA_PACKAGE;
        } else if (packagesSupportingCustomTabs.contains(DEV_PACKAGE)) {
            sPackageNameToUse = DEV_PACKAGE;
        } else if (packagesSupportingCustomTabs.contains(LOCAL_PACKAGE)) {
            sPackageNameToUse = LOCAL_PACKAGE;
        }
        return sPackageNameToUse;
    }

如果把qq浏览器设置为默认，那么这个会返回null。