Question

我有一部分代码在查询数据库后返回一个数组，但是当我运行该应用程序时，它崩溃了

//info is the name of the object of the type DataBase
    info.open();
    String[] data = info.queryAll();
    info.close();

部分数据库代码，我试图检索某列的所有数据库行

public String[] queryAll() {
    String[] columns = new String[] { KEY_NAME };
    Cursor cursor = ourDatabase.query(DATABASE_TABLE, columns, null, null,
            null, null, null);
    if (cursor != null) {
        try {
            final int nameColumnIndex =                     cursor.getColumnIndex(KEY_NAME);
            List<String> names = new ArrayList<String>();
            while (cursor.moveToNext()) {
                names.add(cursor.getString(nameColumnIndex));
            }
            return names.toArray(new String[names.size()]);
        } finally {
            cursor.close();
        }
    }
    return null;

}

是因为我的DataBase在开头是空的吗？如果是这样，我该如何更正代码？所有建议都会有所帮助＆＃39; 谢谢

LOGCAT

09-23 22:26:47.780: E/AndroidRuntime(2825): FATAL EXCEPTION: main
09-23 22:26:47.780: E/AndroidRuntime(2825): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.contactlist/com.example.contactlist.Contacts}: android.database.sqlite.SQLiteException: no such table: mycontacts (code 1): , while compiling: SELECT Contact_name FROM mycontacts
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.app.ActivityThread.access$600(ActivityThread.java:130)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.os.Looper.loop(Looper.java:137)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.app.ActivityThread.main(ActivityThread.java:4745)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at java.lang.reflect.Method.invokeNative(Native Method)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at java.lang.reflect.Method.invoke(Method.java:511)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at dalvik.system.NativeStart.main(Native Method)
09-23 22:26:47.780: E/AndroidRuntime(2825): Caused by: android.database.sqlite.SQLiteException: no such table: mycontacts (code 1): , while compiling: SELECT Contact_name FROM mycontacts
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteDatabase.queryWithFactory(SQLiteDatabase.java:1161)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1032)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.database.sqlite.SQLiteDatabase.query(SQLiteDatabase.java:1200)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at com.example.contactlist.DBContact.queryAll(DBContact.java:97)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at com.example.contactlist.Contacts.onCreate(Contacts.java:38)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.app.Activity.performCreate(Activity.java:5008)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
09-23 22:26:47.780: E/AndroidRuntime(2825):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
09-23 22:26:47.780: E/AndroidRuntime(2825):     ... 11 more

数据库代码

public class DBContact {

    public static final String KEY_ROWID = "_id";
    public static final String KEY_NAME = "Contact_name";
    public static final String KEY_PERSONALPHONE = "Personal_Phonenumber";
    public static final String KEY_HOMEPHONE = "Home_Phonenumber";
    public static final String KEY_OFFICEPHONE = "Office_Phonenumber";

    private static final String DATABASE_NAME = "Contact_name";
    private static final String DATABASE_TABLE = "mycontacts";
    private static final int DATABASE_VERSION = 1;

    // Instance of the class DbHelper
    private DbHelper ourHelper;
    private final Context ourContext;
    private SQLiteDatabase ourDatabase;

    public static final String[] KEYS_ALL = { DBContact.KEY_ROWID,
            DBContact.KEY_NAME, DBContact.KEY_PERSONALPHONE,
            DBContact.KEY_HOMEPHONE, DBContact.KEY_OFFICEPHONE };

    private static class DbHelper extends SQLiteOpenHelper {

        private static final String DATABASE_CREATE = "create table contacts (_id integer primary key autoincrement, "
                + "Contact_name text not null, Personal_Phonenumber text not null, Home_Phonenumber text not null, Office_Phone text not null); ";

        public DbHelper(Context context) {
            super(context, DATABASE_NAME, null, DATABASE_VERSION);
            // TODO Auto-generated constructor stub
        }

        @Override
        public void onCreate(SQLiteDatabase ourDatabase) {
            // TODO Auto-generated method stub
            try {
                ourDatabase.execSQL(DATABASE_CREATE);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }           

        @Override
        public void onUpgrade(SQLiteDatabase ourDatabase, int oldVersion, int newVersion) {
            // TODO Auto-generated method stub
            ourDatabase.execSQL("DROP TABLE IF EXISTS contacts");
            onCreate(ourDatabase);

        }

    }

    // Context of constructor withhin our Class
    public DBContact(Context c) {
        ourContext = c;
    }

    // Opens the database
    public DBContact open() throws SQLException {
        // Constructor for DB Helper class takes in a Context
        // Context is passed in is "ourContext" for within our class

        ourHelper = new DbHelper(ourContext);
        // Passes in DB Name and Version
        // ourDatabase is of type SQLite DataBase
        ourDatabase = ourHelper.getWritableDatabase();
        return this;
    }

    // Closes the database connection
    public void close() {
        // refer to our DbHelper and close the SQLite DataBase Helper
        ourHelper.close();
        ourHelper = null;
        ourDatabase = null;
    }

    // Deletes the Row
    public boolean deleteRow(long rowId) {
        return ourDatabase.delete(DATABASE_TABLE, DBContact.KEY_ROWID + "="
                + rowId, null) > 0;
    }

    public String[] queryAll() {
        String[] columns = new String[] { KEY_NAME };
        Cursor cursor = ourDatabase.query(DATABASE_TABLE, columns, null, null,
                null, null, null);
        if (cursor != null) {
            try {
        final int nameColumnIndex = cursor.getColumnIndex(KEY_NAME);
        List<String> names = new ArrayList<String>();
        cursor.moveToFirst();
        while (cursor.moveToNext()) {
            names.add(cursor.getString(nameColumnIndex));
        }
        return names.toArray(new String[names.size()]);
    } finally {
        cursor.close();
   }
        }
        return null;
    }

    /*public Cursor queryAll(){
    String[] columns = new String[] {KEY_NAME};
        return   ourDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);
    if(data == null){
        columns[0] = "NO CONTACTS PRESENT";
        return columns;
    }else{
        return columns;
    }


    }*/


    public long newRow(String name, String pphone, String hphone, String ophone) {
        // TODO Auto-generated method stub
        ContentValues newvalue = new ContentValues();
        newvalue.put(KEY_NAME, name);
        newvalue.put(KEY_PERSONALPHONE, pphone);
        newvalue.put(KEY_HOMEPHONE, hphone);
        newvalue.put(KEY_OFFICEPHONE, ophone);
        return ourDatabase.insert(DATABASE_TABLE, null, newvalue);

    }



    public String getName(Long l) {
        // TODO Auto-generated method stub
        String[] columns = new String[] { KEY_ROWID, KEY_NAME,
                KEY_PERSONALPHONE, KEY_HOMEPHONE, KEY_OFFICEPHONE };
        Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "="
                + 1, null, null, null, null);
        if (c != null) {
            c.moveToFirst();
            String name = c.getString(1);
            return name;
        }
        return null;
    }

    public String getPphone(Long l) {
        // TODO Auto-generated method stub
        String[] columns = new String[] { KEY_ROWID, KEY_NAME,
                KEY_PERSONALPHONE, KEY_HOMEPHONE, KEY_OFFICEPHONE };
        Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "="
                + 1, null, null, null, null);
        if (c != null) {
            c.moveToFirst();
            String Pphone = c.getString(2);
            return Pphone;

        }
        return null;
    }

    public String getHphone(Long l) {
        // TODO Auto-generated method stub
        String[] columns = new String[] { KEY_ROWID, KEY_NAME,
                KEY_PERSONALPHONE, KEY_HOMEPHONE, KEY_OFFICEPHONE };
        Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "="
                + 1, null, null, null, null);
        if (c != null) {
            c.moveToFirst();
            String Hphone = c.getString(3);
            return Hphone;

        }
        return null;
    }

    public String getOphone(Long l) {
        // TODO Auto-generated method stub
        String[] columns = new String[] { KEY_ROWID, KEY_NAME,
                KEY_PERSONALPHONE, KEY_HOMEPHONE, KEY_OFFICEPHONE };
        Cursor c = ourDatabase.query(DATABASE_TABLE, columns, KEY_ROWID + "="
                + 1, null, null, null, null);
        if (c != null) {
            c.moveToFirst();
            String Ophone = c.getString(4);
            return Ophone;

        }
        return null;
    }
}

Answer 1

您正在创建另一个表

private static final String DATABASE_CREATE = "create table contacts (_id integer  
primary key autoincrement, "
            + "Contact_name text not null, Personal_Phonenumber text not null, 
Home_Phonenumber text not null, Office_Phone text not null); ";

这里是创建联系人表而不是您需要的联系人表

使用

mycontacts

intead of

contacts

Answer 2

在您的create table语句中，您的表名为contacts：

private static final String DATABASE_CREATE = "create table contacts (_id integer primary key autoincrement, "
        + "Contact_name text not null, Personal_Phonenumber text not null, Home_Phonenumber text not null, Office_Phone text not null); ";

然而在你的查询中，它的mycontacts：

private static final String DATABASE_TABLE = "mycontacts";

这可以解释为什么错误告诉您表mycontacts不存在。

尝试将常量更改为：

private static final String DATABASE_TABLE = "contacts";

哪个应该解决这个问题。

Answer 3

您是否创建了mycontacts表，如果没有，则应扩展SQLiteOpenHelper，并覆盖onCreate，如下所示：

        @Override
    public void onCreate(SQLiteDatabase db) {
            db.execSQL("HERE IS YOUR SQL STATEMENT FOR CREATING mycontacts TABLE");
    }

每次需要查询数据库时，都可以使用自己的SQLiteOpenHelper的getReadabledatabase()获取数据库实例;

Answer 4

  private static final String DATABASE_CREATE = "create table contacts (_id integer primary key autoincrement, "
                + "Contact_name text not null, Personal_Phonenumber text not null, Home_Phonenumber text not null, Office_Phone text not null); ";

Office_Phone中的上述代码与声明不匹配。也是别人说的。

SQLite数据库后的应用程序崩溃

4 个答案: