Use Chrome Custom Tabs when possible

[lbalmaceda]

This PR adds support for Chrome Custom Tabs to use with the WebAuthProvider class when not launching a WebView. The user API remains the same, but now they need a different configuration and they can skip the call to WebAuthProvider.resume(intent) as it's handled internally by the library. This also means that they don't need to capture the onNewIntent or onActivityResult method calls.

Proposed configuration changes

1. Remove the custom Intent-Filter that captures the Callback URI from the AndroidManifest.xml file.

2a. Add both manifestPlaceholders to the app/build.gradle file so that the library knows which domain and scheme to use. The host is set automatically using the applicationId placeholder:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.3"
    defaultConfig {
        applicationId "com.auth0.samples"
        minSdkVersion 15
        targetSdkVersion 25
        manifestPlaceholders = [auth0Domain: "@string/auth0_domain", auth0Scheme: "https"]
    }
//...
}

2b. Alternatively, don't set the manifestPlaceholders but replace the RedirectActivity definition in the AndroidManifest.xml file with one that defines the custom Intent-Filter.

<activity android:name="com.auth0.android.provider.RedirectActivity">
<intent-filter>
                <action android:name="android.intent.action.VIEW" />
                <category android:name="android.intent.category.DEFAULT" />
                <category android:name="android.intent.category.BROWSABLE" />

                <data
                    android:host="@string/auth0_domain"
                    android:pathPrefix="/android/{YOUR_APP_PACKAGE_NAME}/callback"
                    android:scheme="https" />
            </intent-filter>
</activity>

Not setting the placeholders like in (2a) or not overriding the Intent-Filter declaration like in (2b) will result in the library's defined Intent-Filter to not find the expected placeholder values and the code to not compile.

Discussion

The trade-off is between setting a default https scheme in the library's Intent-Filter (so the user doesn't need to set an extra manifest placeholder) or setting a placeholder that the user must always define.

If a normal user will use more https over a custom scheme, we can let them override the whole Intent-Filter in the manifest like in (2b). If a normal user will prefer custom schemes, then we can keep the 2 manifest placeholders proposal.

[hzalaz]

Alternatively you can declare the RedirectActivity in the AndroidManifest.xml file with your own intent-filter so it overrides the library's default.

[hzalaz]

If we promote https and is the best UX we can make it the default in the library, remove the placeholder and let the user declare the whole activity if he needs custom schemes.

[lbalmaceda]

Another thing with the usage of placeholders: If the user doesn't want to use WebAuthProvider and just uses the AuthenticationAPIClient (i.e. for createUser/login) then the compiler will force him to set a valid placeholder anyway.

[nikolaseu]

I think the negation is wrong?

[nikolaseu]

I mean
"launch uri if service was already bound or was just bounded successfully"
but then.. why call bindService if it was already bound?

[nikolaseu]

anybody cares if it was already bound or was bound in this call?

[nikolaseu]

ok I get it.
but from the way it's used, this can never be "already bound" because a new controller is created each time. maybe something to optimize in the activity that uses this in https://github.com/auth0/Auth0.Android/pull/95/files#diff-101f8235cd64f6d21cfc3fc82d610bd5R105

[nikolaseu]

should this be also cleared when the uri is launched?

[lbalmaceda]

I decided to go with the default https scheme option. On my tests with the different emulators, the longer it took to bind and connect to the Custom Tabs Service was ~600ms. I've set a max non-blocking wait time of 1 second for the service to connect, that IMHO could be raised to 1.5 or 2 safely. If the service is not connected in that given time, a call to launchUri will use a simple Browser instead of the Custom Tabs Browser.