通过JDBC连接Android Studio和(本地) mySql服务器

Question

我正在尝试连接我的安卓应用程序与我的本地MySQL数据库，然后获得一些内容的数据库与JDBC。因此，我尝试使用以下代码连接到数据库：

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();
        }

我在清单中给了互联网权限(<uses-permission android:name="android.permission.INTERNET"/>)

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

当我想要启动它时，我得到了这个错误：

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:\Users\Alexander\Desktop\Programmierung\Testing2\app\libs\mysql-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

这听起来像是我必须将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:\Users\Alexander\Desktop\Programmierung\Testing2\app\libs\mysql-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?

但不管怎么说，我觉得我的方式是完全错误的。有人知道我该怎么做了。

Answer 1

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