ParsingPlayer | video player playing videos from youku.com and other video | Video Utils library

First, I have to tell you that it is not recommended to ask two questions at once via StackOverflow, mainly because it may be hard to choose a correct answer, if two answers help you with the different questions you asked.

Anyhow, I'll try to answer both of your questions:

To use an additional properties file (local.properties in your case) is not a Gradle approach. It is in fact pure Java. You should only read properties on your own in very rare cases and never in a build script. If you really need an additional properties file, develop a Gradle plugin, which handles the file access.

Gradle automatically reads the gradle.properties file, but not only in the project directory, but also in the user-specific gradle home directory (e.g. C:\Users\**\.gradle). This is helpful to define private data, which won't find its way into version control, even if you forget to ignore the files manually. The defined data will be accessible to any project.

Well, I assume the file local.properties does not exist, because you did neither put it under version control nor let your CI add it automatically. Where should the login data come from?

The solution is simple. Just add the required data to the CI user gradle home directories (e.g. /home/travis/.gradle) gradle.properties file. This way, you can also simply add access right management, by entering the login data of a CI user. Local builds will be published by your local user account (if allowed), CI builds by the CI system.

Your question includes the Gradle specific term 'extension', but, to be honest, it got nothing to do with your question. It is correct, that most configuration in Gradle is done via so-called extension objects, that are added to the Project object, but it is an internal term, you do not need to understand it to fix this problem.

Now I can understand your confusion. Gradle distinguishes between the configuration phase and the execution phase. Nearly everything in your build script is executed during the configuration phase, only task actions (what a task does, e.g. copying, deleting ...), doFirst and doLast closures (so basically tasks) are executed during execution phase. If you define the list of tasks to be executed (via command line), it only affects the execution phase, but your configuration code will be executed at every single build, even if only one independent task is executed afterwards.

To solve this problem, follow the solution in the First block and add your private data to the user-specific Gradle directory gradle.properties file. It will be added to the project object and therefor, it will be accessible from the build file. But, since the file (or the data) does not exist on your CI, accessing it directly will raise an error when building on the CI. You can use the findProperty(propertyName) method as a fail-safe way to access the property value. If the property does not exist, it returns null (in the configuration phase), so no error occurs, as long as you don not execute the bintrayUpload task (which is not your goal on the CI).