java - 解决 java.lang.NoClassDefFoundError

Question

我有这门课

public class DaoMaster extends AbstractDaoMaster {
    public static final int SCHEMA_VERSION = 1605131322;

    /** Creates underlying database table using DAOs. */
    public static void createAllTables(SQLiteDatabase db, boolean ifNotExists) {
        ApplicationConfigDao.createTable(db, ifNotExists);
        RequestCacheDao.createTable(db, ifNotExists);
    }

    /** Drops underlying database table using DAOs. */
    public static void dropAllTables(SQLiteDatabase db, boolean ifExists) {
        ApplicationConfigDao.dropTable(db, ifExists);
        RequestCacheDao.dropTable(db, ifExists);
    }

    public static abstract class OpenHelper extends SQLiteOpenHelper {

        public OpenHelper(Context context, String name, CursorFactory factory) {
            super(context, name, factory, SCHEMA_VERSION);
        }

        @Override
        public void onCreate(SQLiteDatabase db) {
            Log.i("greenDAO", "Creating tables for schema version " + SCHEMA_VERSION);
            createAllTables(db, false);
        }
    }

    /** WARNING: Drops all table on Upgrade! Use only during development. */
    public static class DevOpenHelper extends OpenHelper {

        public DevOpenHelper(Context context, String name, CursorFactory factory) {
            super(context, name, factory);
        }

        @Override
        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            Log.i("greenDAO", "Upgrading schema from version " + oldVersion + " to " + newVersion + " by dropping all tables");
            dropAllTables(db, true);
            onCreate(db);
        }
    }

    public DaoMaster(SQLiteDatabase db) {
        super(db, SCHEMA_VERSION);
        registerDaoClass(ApplicationConfigDao.class);
        registerDaoClass(RequestCacheDao.class);
    }

    public DaoSession newSession() {
        return new DaoSession(db, IdentityScopeType.Session, daoConfigMap);
    }

    public DaoSession newSession(IdentityScopeType type) {
        return new DaoSession(db, type, daoConfigMap);
    }    
}

然后是另一个类

更新正如你们中的一些人所指出的，我的命名约定似乎很糟糕，这是一个多么愚蠢的基本错误，所以我将它们更新为以下内容

public class DbHelper {
    public static final String LOGIN_DATA_PREFIX = "LOGIN_DATA_";
    public DaoMaster DAOMaster;
    public DaoSession DAOSession;
    public DaoMaster.OpenHelper openHelper;
    public SQLiteDatabase SQLiteDb;

    private Context context;

    public static class CONSTANT {
        public static String DB_FILE_NAME = "app.db";

        /* Define all DAO Property Constant Here */

        public static class APPLICATION_CONFIG {
            public static String DAO_NAME = "applicationconfig";
            public static String PROPERTY_ID = "Id";
            public static String PROPERTY_KEY = "Key";
            public static String PROPERTY_VALUE = "Value";
        }

        public static class REQUEST_CACHE{
            public static String DAO_NAME = "requestcache";
            public static String PROPERTY_URL = "Url";
            public static String PROPERTY_METHOD = "Method";
            public static String PROPERTY_PARAM = "Param";
            public static String PROPERTY_ID = "Id";
        }

        //...

    }

    public class DAOWrapper {
        private DaoSession session;

        /* Load all DAO Here */
        public ApplicationConfigDao ApplicationConfig;
        public RequestCacheDao RequestCache;
        // ...

        public DAOWrapper(DaoSession session){
            this.session = session;

            /* Init all DAO Here */
            this.ApplicationConfig = this.session.getApplicationConfigDao();
            this.RequestCache = this.session.getRequestCacheDao();
            // ...
        }
    }

    public DAOWrapper DAO;

    public DbHelper(Context context){
        this.context = context;
        this.openHelper = new DaoMaster.DevOpenHelper(this.context, CONSTANT.DB_FILE_NAME, null);
        this.SQLiteDb = this.openHelper.getWritableDatabase();
        this.DAOMaster = new DaoMaster(this.SQLiteDb);
        this.DAOSession = this.DAOMaster.newSession();
        this.DAO = new DAOWrapper(this.DAOSession);
    }

    ...
}

但还是失败

然后初始化类

this.Db = new DbHelper(this.getApplicationContext());

但是在创建实例DaoMaster.DevOpenHelper的过程中抛出错误，据说找不到类DevOpenHelper，我的代码有什么问题吗？

更新错误控制台

5-15 23:22:31.313  20424-20424/com.itp.android.suitetreatadmin E/dalvikvm﹕ Could not find class 'com.itp.android.suitetreatadmin.dao.DaoMaster$DevOpenHelper', referenced from method com.itp.android.suitetreatadmin.DbHelper.<init>
05-15 23:22:44.190  20424-20424/com.itp.android.suitetreatadmin E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.itp.android.suitetreatadmin, PID: 20424
    java.lang.NoClassDefFoundError: com.itp.android.suitetreatadmin.dao.DaoMaster$DevOpenHelper
            at com.itp.android.suitetreatadmin.DbHelper.<init>(DbHelper.java:86)
            at com.itp.android.suitetreatadmin.App.onCreate(App.java:108)
            at android.app.Instrumentation.callApplicationOnCreate(Instrumentation.java:1007)
            at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4328)
            at android.app.ActivityThread.access$1500(ActivityThread.java:135)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5001)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)

我知道有一些类似的问题，但我认为这是个案问题，

感谢您的帮助。

Answer 1

在 DbHelper 类中，你不能给对象名和类名一样，所以你必须像这样更改对象名

DaoMaster daoMaster;
DaoSession daoSession;