android JDBC mysql java connector app:preDexDebug

Question

Im trying to learn how to use the JDBC to connect a application to a mysql database.
Im using the Android Studio.
I downloaded \"mysql-connector-java-5.1.37\" f

Answer 1

Try to sync your project Tools -> Android -> Sync Project with Gradle Files

And then rebuild your project: build -> rebuild project

Answer 2

I had the same issue and the problem was in the mysql-connector-java-5.1.37.jar file. I downloaded an older version (mysql-connector-java-3.0.17-ga-bin.jar) from here and worked like a charm.

To get the connection use:

Class.forName("com.mysql.jdbc.Driver").newInstance();
String connection = "jdbc:mysql://"+ your_ip + ":"+ your_port +"/"+ database_name;
conn = DriverManager.getConnection(connection, user, pass); 

Just in case, don't forget to compile it in your build.gradle:

dependencies {
    //other stuff
    compile files('libs/mysql-connector-java-3.0.17-ga-bin.jar')
}

PD: This only works if you use the connection from and AsyncTask

Answer 3

Because Distributed mysql-connector-java-5.1.37-bin.jar is compiled for Java1.8, current Android dex compiler cannot recognize it.

$ javap -v com/mysql/jdbc/JDBC42Helper.class| grep "major version"
  major version: 52

On the oher hand, mysql-connector-java-5.1.36.jar is compiled for Java1.6.

$ javap -v com/mysql/jdbc/JDBC4Connection.class |grep "major version"
  major version: 50

5.1.37 supports JDBC4.2, so requires Java1.8.