Question

我是一名Windows手机开发者，是Android数据库的新手，我无法在android中创建本地数据库我无法理解我在哪里做错了

我将在我的数据库中存储一些数据，稍后将获取它以填充我的列表视图。

目前我无法创建示例数据库，下面是我的代码

public final class DbContract {

public DbContract() {
}

private static final String TEXT_TYPE = " TEXT";
private static final String COMMA_SEP = ",";
private static DatabaseHelper dbHandler;
Context context;

public DatabaseHelper database;

/* Inner classes that defines the all table contents */

/**
 * Hospital database structure, query
 * */

public static abstract class Hospital implements BaseColumns {
    public static final String TABLE_NAME = "emergency_hospital";
    public static final String HOSPITAL_NAME = "name";
    public static final String HOSPITAL_ADDRESS = "address";
    public static final String HOSPITAL_CONTACT_NUMBER = "number";

}

private static final String SQL_CREATE_EMERGENCY_HOSPITAL = "CREATE TABLE "
        + Hospital.TABLE_NAME + " (" + Hospital._ID
        + " INTEGER PRIMARY KEY," + Hospital.HOSPITAL_NAME + TEXT_TYPE
        + COMMA_SEP + Hospital.HOSPITAL_ADDRESS + TEXT_TYPE + COMMA_SEP
        + Hospital.HOSPITAL_CONTACT_NUMBER + TEXT_TYPE + COMMA_SEP + " );";

private static final String SQL_DELETE_EMERGENCY_HOSPITAL = "DROP TABLE IF EXISTS "
        + Hospital.TABLE_NAME;

/**
 * Handles database versions, create and populate tables in database
 **/

public class DatabaseHelper extends SQLiteOpenHelper {

    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_NAME = "sample.db";

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

    public void onCreate(SQLiteDatabase db) {
        db.execSQL(SQL_CREATE_EMERGENCY_HOSPITAL);
    }

    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // This database is only a cache for online data, so its upgrade
        // policy is
        // to simply to discard the whole database and start over
        db.execSQL(SQL_DELETE_EMERGENCY_HOSPITAL);
        onCreate(db);
    }


}

public static DatabaseHelper getDbHandler() {
    return dbHandler;
}

public void HospitalData() {
    // Gets the data repository in write mode
    SQLiteDatabase db = database.getWritableDatabase();

    // Create a new map of values, where column names are the keys
    ContentValues values = new ContentValues();

    values.put(Hospital.HOSPITAL_NAME, "Bellevue Hospital Centre");
    values.put(Hospital.HOSPITAL_ADDRESS, "Manhattan");
    values.put(Hospital.HOSPITAL_CONTACT_NUMBER, "4356754");

    // Insert the new row, returning the primary key value of the new row
    long newRowId;

    newRowId = db.insert(Hospital.TABLE_NAME, null, values);
}

}

在我的主要活动中

private static DatabaseHelper dbHelper;
private SQLiteDatabase db;
dbHelper = DbContract.getDbHandler();
    db = dbHelper.getReadableDatabase();

我的清单上写着

<provider
        android:name=".database.DbContract"
        android:authorities="com.demo" >
    </provider>

这是初始化数据库创建的正确方法吗？

 E/AndroidRuntime(2069): java.lang.RuntimeException: Unable to get provider com.demo.database.DbContract: java.lang.ClassCastException: com.demo.database.DbContract cannot be cast to android.content.ContentProvider

 E/AndroidRuntime(2069):    at           com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
  E/AndroidRuntime(2069): Caused by: java.lang.ClassCastException:        com.demo.database.DbContract cannot be cast to android.content.ContentProvider

谢谢！

Answer 1

您的mainfest文件包含名称为“.database.DbContract”的提供程序标记。这是您获得异常的根本原因。提供者标记用于声明内容提供者，名称标记可以是内容提供者的包名称，但在您的情况下，它不是任何内容提供者子类的名称。因此获得类强制转换异常。请阅读内容提供者的基础知识： http://developer.android.com/guide/topics/providers/content-provider-basics.html

希望对你有帮助!!!

数据库创建不工作android

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