通过 JDBC 将 Android Studio 与(本地)mySql Server 连接

Question

我正在尝试将我的Android应用程序与本地MySQL数据库连接，然后使用JDBC获取数据库的一些内容。所以我尝试了这段代码来连接到数据库：

try{
Class.forName("com.mysql.jdbc.Driver");
Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/rpg","root", "whatever");
Statement statement = connection.createStatement();
final ResultSet resultSet = statement.executeQuery("select * from player");
Log.i("Content",resultSet.getString(0));
}catch (Exception e) {
e.printStackTrace();
}

我在清单中给予了互联网许可 (<uses-permission android:name="android.permission.INTERNET"/>(

并将mySQL连接器实现为库(mysql-connector-java-8.0.12.jar(。

当我想启动它时，出现此错误：

Default interface methods are only supported starting with Android N (--min-api 24): void com.mysql.cj.protocol.AuthenticationPlugin.destroy()  
Default interface methods are only supported starting with Android N (--min-api 24): void com.mysql.cj.protocol.MessageSender.send(com.mysql.cj.protocol.Message)   
Default interface methods are only supported starting with Android N (--min-api 24): byte com.mysql.cj.protocol.MessageReader.getMessageSequence()  
Default interface methods are only supported starting with Android N (--min-api 24): com.mysql.cj.result.Row com.mysql.cj.result.RowList.get(int)   
Default interface methods are only supported starting with Android N (--min-api 24): com.mysql.cj.protocol.Message com.mysql.cj.interceptors.QueryInterceptor.postProcess(com.mysql.cj.protocol.Message, com.mysql.cj.protocol.Message) 
null    
com.android.builder.dexing.DexArchiveBuilderException: Failed to process C:UsersAlexanderDesktopProgrammierungTesting2applibsmysql-connector-java-8.0.12.jar    
com.android.builder.dexing.DexArchiveBuilderException: Error while dexing.  
com.android.tools.r8.CompilationFailedException: Compilation failed to complete 
com.android.tools.r8.utils.AbortException

这听起来像我必须将 minSdkVersion 增加到 24 对吧？所以我这样做了，然后出现了这个错误：

Invoke-customs are only supported starting with Android O (--min-api 26)    
null    
com.android.builder.dexing.DexArchiveBuilderException: Failed to process C:UsersAlexanderDesktopProgrammierungTesting2applibsmysql-connector-java-8.0.12.jar
com.android.builder.dexing.DexArchiveBuilderException: Error while dexing.  
com.android.tools.r8.CompilationFailedException: Compilation failed to complete 
com.android.tools.r8.utils.AbortException   

所以我也把它增加到 26，然后得到这个错误：

Installation failed with message INSTALL_FAILED_OLDER_SDK: Failed parse during installPackageLI: /data/app/vmdl127069021.tmp/base.apk (at Binary XML file line #7): Requires newer sdk version #26 (current version is #25).
It is possible that this issue is resolved by uninstalling an existing version of the apk if it is present, and then re-installing.
WARNING: Uninstalling will remove the application data!
Do you want to uninstall the existing application?

但无论如何，感觉我完全错了。有人知道我该怎么做。

Answer 1

在

• 项目窗口中打开build.gradle(模块：应用程序(
• 将minSdkVersion更改为 24 或更高