Leadbord数据库

时间：2013-01-17 17:10:37

标签： android sql

这实际上是我第一次尝试在android上使用SQL数据库。所以我希望你能帮助我。 我目前正在为我们的游戏中的一个领导者工作，并希望为它编写通信类，但我遇到了麻烦。我使用了http://www.vogella.com/articles/AndroidSQLite/article.html。这就是我的Db助手课程的样子

public class MySQLiteHelper extends SQLiteOpenHelper {

public static final String TABLE_LEADBOARD = "leadboard";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_NAME = "name";
public static final String COLUMN_LEVEL = "level";
public static final String COLUMN_KILLPOINTS = "killpoints";

private static final String DATABASE_NAME = "leadboard.db";
private static final int DATABASE_VERSION = 1;

// Database creation sql statement
private static final String DATABASE_CREATE = "create table "
    + TABLE_LEADBOARD + "(" + COLUMN_ID
    + " integer primary key autoincrement, " + COLUMN_NAME
    + " text,"+ COLUMN_LEVEL + " integer," +COLUMN_KILLPOINTS + " integer);";

public MySQLiteHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase database) {
    database.execSQL(DATABASE_CREATE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    Log.w(MySQLiteHelper.class.getName(),
            "Upgrading database from version " + oldVersion + " to "
                    + newVersion + ", which will destroy all old data");
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_LEADBOARD);
    onCreate(db);
}
}

我写了一个简单的元素，它有4个字段，getter和setter 

public class LeadbordElement {
    private long id;
    private int level;
    private int killPoints;
    private String name;

我的连接类现在看起来像这样

public class DatabaseCommunication {
    // Database fields
    private SQLiteDatabase database;
    private MySQLiteHelper dbHelper;
    // all columns for the query
    private String[] allColumns = { MySQLiteHelper.COLUMN_ID,
            MySQLiteHelper.COLUMN_NAME, MySQLiteHelper.COLUMN_LEVEL,
            MySQLiteHelper.COLUMN_KILLPOINTS };

    public DatabaseCommunication(Context context) {
        dbHelper = new MySQLiteHelper(context);
    }

    public void open() throws SQLException {
        database = dbHelper.getWritableDatabase();
    }

    public void close() {
        dbHelper.close();
    }

    /**
     * Save element to database
     * 
     * @author Benjamin M. 17.01.2013
     * @param element
     */
    public void addLeadbordElement(LeadbordElement element) {
        this.open();
        ContentValues values = new ContentValues();
        values.put(MySQLiteHelper.COLUMN_NAME, element.getName());
        values.put(MySQLiteHelper.COLUMN_LEVEL, element.getLevel());
        values.put(MySQLiteHelper.COLUMN_KILLPOINTS, element.getKillPoints());
        database.insert(MySQLiteHelper.TABLE_LEADBOARD, null, values);
        this.close();
    }

    /**
     * Methode to get a Vektor of elements
     * 
     * @author Benjamin M. 17.01.2013
     */
    public Vector<LeadbordElement> getTop10() {
        this.open();
        // should return ordert by killpoints
        Cursor cursor = database.query(MySQLiteHelper.TABLE_LEADBOARD,
                allColumns, null, null, null, null,
                MySQLiteHelper.COLUMN_KILLPOINTS + " DESC");

        Vector<LeadbordElement> elements = new Vector<LeadbordElement>();

        //creating the vector of elements
        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            elements.add(this.createElement(cursor));
            cursor.moveToNext();
        }
        cursor.close();
        this.close();
        return elements;
    }

    /**
     * Methode to create a LeadbordElement out of the cursor
     * 
     * @author Benjamin M. 17.01.2013
     * @param cursor
     * @return
     */
    private LeadbordElement createElement(Cursor cursor) {
        LeadbordElement element = new LeadbordElement();
        element.setId(cursor.getLong(0));
        element.setName(cursor.getString(1));
        element.setLevel(cursor.getInt(2));
        element.setKillPoints(cursor.getInt(3));
        return element;
    }
}

但这实际上并不起作用。我不能像这样得到它的前十名，我不会得到它的错误。实际上，我可以创建DatabaseCommunication，我可以添加一个元素。不确定它是否真的被添加到数据库中。但我不能让那些回来。 它说没有Column：level :,编译时：select _id .......

至少我有一个textview并希望在那里显示元素。

谢谢，如果你能提供帮助！

错误日志：

01-17 19:04:35.920: E/AndroidRuntime(1428): FATAL EXCEPTION: main
01-17 19:04:35.920: E/AndroidRuntime(1428): java.lang.IllegalStateException: Could not execute method of the activity
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.view.View$1.onClick(View.java:3044)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.view.View.performClick(View.java:3511)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.view.View$PerformClick.run(View.java:14110)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.os.Handler.handleCallback(Handler.java:605)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.os.Looper.loop(Looper.java:137)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.app.ActivityThread.main(ActivityThread.java:4424)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at java.lang.reflect.Method.invokeNative(Native Method)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at java.lang.reflect.Method.invoke(Method.java:511)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at dalvik.system.NativeStart.main(Native Method)
01-17 19:04:35.920: E/AndroidRuntime(1428): Caused by: java.lang.reflect.InvocationTargetException
01-17 19:04:35.920: E/AndroidRuntime(1428):     at java.lang.reflect.Method.invokeNative(Native Method)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at java.lang.reflect.Method.invoke(Method.java:511)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.view.View$1.onClick(View.java:3039)
01-17 19:04:35.920: E/AndroidRuntime(1428):     ... 11 more
01-17 19:04:35.920: E/AndroidRuntime(1428): Caused by: android.database.sqlite.SQLiteException: no such column: level: , while compiling: SELECT _id, name, level, killpoints FROM leadboard ORDER BY killpoints DESC
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteCompiledSql.native_compile(Native Method)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteCompiledSql.<init>(SQLiteCompiledSql.java:68)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteProgram.compileSql(SQLiteProgram.java:143)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteProgram.compileAndbindAllArgs(SQLiteProgram.java:361)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:127)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:94)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:53)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:47)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1564)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1449)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1405)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1485)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at control.database.DatabaseCommunication.getTop10(DatabaseCommunication.java:61)
01-17 19:04:35.920: E/AndroidRuntime(1428):     at com.main.MainActivity.startLeadbord(MainActivity.java:178)
01-17 19:04:35.920: E/AndroidRuntime(1428):     ... 14 more

1 个答案:

答案 0 :(得分：1)

我认为我看到它...请在COLUMN_LEVEL和COLUMN_KILLPOINTS

之后添加一个（缺少的）空格

...从

private static final String DATABASE_CREATE = "create table "
    + TABLE_LEADBOARD + "(" + COLUMN_ID
    + " integer primary key autoincrement, " + COLUMN_NAME
    + " text,"+ COLUMN_LEVEL + "integer," +COLUMN_KILLPOINTS + "integer);";

于... 

private static final String DATABASE_CREATE = "create table "
    + TABLE_LEADBOARD + "(" + COLUMN_ID
    + " integer primary key autoincrement, " + COLUMN_NAME
    + " text,"+ COLUMN_LEVEL + " integer," +COLUMN_KILLPOINTS + " integer);";
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