java.lang.ClassNotFoundException: org.postgresql.Driver, Android

Solution 1:

You need to add the PostgreSQL JDBC Driver in your project as mentioned in search.maven.org.

Gradle:

implementation 'org.postgresql:postgresql:42.2.10'

Maven:

<dependency>
  <groupId>org.postgresql</groupId>
  <artifactId>postgresql</artifactId>
  <version>42.2.10</version>
</dependency>

You can also download the JAR and import to your project manually.

NOTE: Compile as used in this answer is deprecated. Replace with implementation as per 3.

Solution 2:

You should put the jar package into the lib folder(WebContent-WEB-INF-lib),and right click on the jar package-build path-add to build path