从SQLite数据库读取会导致堆栈溢出

时间：2015-05-29 15:27:54

标签： android sqlite

无法找到为什么SQLite数据库无法读取的问题，它花了我这么久，我仍然无法弄清楚为什么尝试从中读取它给我堆栈溢出，感谢所有帮助，谢谢。 

public class DatabaseHandler extends SQLiteOpenHelper {


private static Context ctx;


// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;

// Database Name
private static final String DATABASE_NAME = "chirhogs_android_api";

// Login table name
private static final String TABLE_LOGIN = "fusers";

// Login Table Columns names
private static final String KEY_ID = "id";
public static final String KEY_NAME = "name";
public static final String KEY_EMAIL = "email";
private static final String KEY_UID = "uid";
private static final String KEY_CREATED_AT = "created_at";

public DatabaseHandler(Context ctx) {
    super(ctx, DATABASE_NAME, null, DATABASE_VERSION);
    this.ctx = ctx;

}

DatabaseHandler jhelper = new DatabaseHandler(ctx.getApplicationContext());

// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
    String CREATE_LOGIN_TABLE = "CREATE TABLE " + TABLE_LOGIN + "("
            + KEY_ID + " INTEGER PRIMARY KEY," 
            + KEY_NAME + " TEXT,"
            + KEY_EMAIL + " TEXT UNIQUE,"
            + KEY_UID + " TEXT,"
            + KEY_CREATED_AT + " TEXT " + ");";
    db.execSQL(CREATE_LOGIN_TABLE);
}

// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // Drop older table if existed
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_LOGIN);

    // Create tables again
    onCreate(db);
}

/**
 * Storing user details in database
 * */
public void addUser(String name, String email, String uid, String created_at) {
    SQLiteDatabase db = jhelper.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put(KEY_NAME, name); // Name
    values.put(KEY_EMAIL, email); // Email
    values.put(KEY_UID, uid); // Email
    values.put(KEY_CREATED_AT, created_at); // Created At

    // Inserting Row
    db.insert(TABLE_LOGIN, null, values);
     // Closing database connection
}

/**
 * Getting user data from database
 * */
public HashMap<String, String> getUserDetails(){
    HashMap<String,String> user = new HashMap<String,String>();
    String selectQuery = "SELECT  * FROM " + TABLE_LOGIN + " ORDER BY "+KEY_CREATED_AT+" DESC LIMIT 1";

    SQLiteDatabase db = jhelper.getReadableDatabase();

    Cursor cursor = db.rawQuery(selectQuery, null);
    // Move to first row
    cursor.moveToFirst();
    if(cursor.getCount() > 0){
        user.put("name", cursor.getString(1));
        user.put("email", cursor.getString(2));
        user.put("uid", cursor.getString(3));
        user.put("created_at", cursor.getString(4));
    }
    cursor.close();
    db.close();
    // return user
    return user;
}

/**
 * Getting user login.xml status
 * return true if rows are there in table
 * */
public int getRowCount() {
    String countQuery = "SELECT  * FROM " + TABLE_LOGIN;
    SQLiteDatabase db = jhelper.getReadableDatabase();
    Cursor cursor = db.rawQuery(countQuery, null);
    int rowCount = cursor.getCount();

    cursor.close();

    // return row count
    return rowCount;
}

当我运行它时，它给我堆栈溢出并关闭应用程序，我检查了SQLite数据库并且数据写得正确，这只是读数问题。

这是日志：

05-29 15:15:59.827    3191-3191/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: abelabs.dank, PID: 3191
java.lang.StackOverflowError: stack size 8MB
        at android.database.sqlite.SQLiteOpenHelper.<init>(SQLiteOpenHelper.java:77)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:35)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.dank.library.DatabaseHandler.<init>(DatabaseHandler.java:38)
        at abelabs.

1 个答案:

答案 0 :(得分：3)

这是因为这一行：

DatabaseHandler jhelper = new DatabaseHandler(ctx.getApplicationContext());

每次创建DatabaseHandler类的新实例时，它都会创建一个新实例，从而创建一个新实例，依此类推。摆脱该行并将所有jhelper引用替换为this。

修改

通常，当我使用DatabaseHelper时，我通过使DatabaseHandler成为单例来实现它。

private static DatabaseHelper sDatabaseHelperInstance = null;

public static DatabaseHelper getInstance(Context context)
{
    if (sDatabaseHelperInstance == null)
    {
        sDatabaseHelperInstance = new DatabaseHelper(context);
    }
    return sDatabaseHelperInstance;
}

然后，只要你需要一个SQLiteDatabase实例，你就可以得到如下：

SQLiteDatabase db = DatabaseHelper.getInstance(some context object).getReadableDatabase();

对于getRowCount()和getUserDetails()等方法，您必须为他们提供Context参数。

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