Android App无法创建数据库/在文件资源管理器中找不到它-DDMS

Question

因此，我创建了一个应该创建数据库的应用程序。 但是，我查看了ADM，但发现它不在其中。

我的困惑是为什么不创建它？ 我有：

1. 数据库处理程序
2. MyActivity.java
3. 汽车.java

我从MyActivity内部的DatabaseHandler.java调用方法。 我的项目中有0个错误。

这是我的DatabaseHandler.java：

package com.example.brad.myapplication;

import android.accounts.Account;
import android.database.DatabaseUtils;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.net.Uri;

import static android.database.DatabaseUtils.dumpCursorToString;

/**
 * Created by Brad on 19/07/2014.
 */
public class DatabaseHandler extends SQLiteOpenHelper {

   private static final int DATABASE_VERSION = 1;
   private static final String DATABASE_NAME = "carsGrid",
    TABLE_CARS = "cars",
    KEY_ID = "id",
    KEY_POSTCODE = "postcode",
    KEY_ADDRESS = "address",
    KEY_IMAGE = "image";

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE" + TABLE_CARS + ")" + KEY_ID + "INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_ADDRESS + " TEXT,"+  KEY_POSTCODE + " TEXT," + KEY_IMAGE  + " TEXT)");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_CARS);

        onCreate(db);
    }

    public void createCar(Car car) {
        SQLiteDatabase db = getWritableDatabase();

        ContentValues values = new ContentValues();

        values.put(KEY_ADDRESS, car.get_address());
        values.put(KEY_POSTCODE, car.get_postcode());
        values.put(KEY_IMAGE, car.get_image());

        db.insert(TABLE_CARS, null, values);
        db.close();
    }

    public Car getCar(int id) {
        SQLiteDatabase db = getReadableDatabase();

        Cursor cursor = db.query(TABLE_CARS, new String[] {KEY_ID, KEY_IMAGE, KEY_ADDRESS, KEY_POSTCODE}, KEY_ID + "=?", new String[] { String.valueOf(id)}, null,null,null,null);

        if (cursor != null)
            cursor.moveToFirst();

        Car car = new Car(Integer.parseInt(cursor.getString(0)), cursor.getString(1), cursor.getString(2),cursor.getString(3));
        return car;
    }

    public int getCarCount() {
        //SELECT * FROM CARS
        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor = db.rawQuery("SELECT * FROM" + TABLE_CARS, null);
        cursor.close();

        return cursor.getCount();
    }

    public String getRandomImageKey() {
        //SELECT * FROM CARS
        SQLiteDatabase db = getReadableDatabase();
        Cursor cursor = db.rawQuery("SELECT " + KEY_ID + "," + KEY_IMAGE + " FROM" + TABLE_CARS + "ORDER BY RANDOM() LIMIT 1", null);
        int columnIndex = cursor.getColumnIndex(KEY_ID);
        String toReturn = cursor.getString(columnIndex);
        return toReturn;
    }

    public Car getCurrentCar() {

        SQLiteDatabase db       =   getWritableDatabase();
        String sql              =   "SELECT " + KEY_ID + "," + KEY_IMAGE + " FROM " + TABLE_CARS + "ORDER BY RANDOM() LIMIT 1";
        Cursor cursor           =   db.rawQuery(sql, new String[] {});
        Car car = null;

        try {
            if (cursor.moveToFirst()) {
                car = new Car(Integer.parseInt(cursor.getString(0)), cursor.getString(1), cursor.getString(2), cursor.getString(3));
            }
        }
        finally {
            if (cursor != null && !cursor.isClosed()) {
                cursor.close();
            }
                db.close();
        }
        return car;
    }

}

这是我的MyActivity.java：

public class MyActivity extends Activity {


    // Defining elements in XML
    EditText postCodeStringTxt, DistanceNumberTxt, DebugCarTxt;
    String imagestring;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);

        // Creating elements in XML
        postCodeStringTxt = (EditText) findViewById(R.id.postCodeString);
        DistanceNumberTxt = (EditText) findViewById(R.id.DistanceNumber);
        DebugCarTxt = (EditText) findViewById(R.id.DebugCar);

        // you should  instantiate 'DatabaseHandler'  here
        DatabaseHandler db = new DatabaseHandler(this); // "this" refer to the context
        Car cars = db.getCurrentCar();

        db.createCar(new Car(cars.get_id(),cars.get_address(),cars.get_postcode(),cars.get_image()));
        String rows= "id : "+ cars.get_id()+ " address : "+cars.get_address() + "postcode : "+cars.get_postcode()+" image : "+cars.get_image();

如果项目中没有错误，如何将区域划分为无效区域？

Answer 1

使用以下更改您的Create Table SQL Command ：

    db.execSQL("CREATE TABLE" + TABLE_CARS + "(" + KEY_ID + "INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_ADDRESS + " TEXT,"+  KEY_POSTCODE + " TEXT," + KEY_IMAGE  + " TEXT)");

未创建数据库是因为创建Table SQL Command Syntax错误。

你也应该改变这个

  Cursor cursor = db.rawQuery("SELECT " + KEY_ID + "," + KEY_IMAGE + " FROM" + TABLE_CARS + "ORDER BY RANDOM() LIMIT 1", null);

至

  Cursor cursor = db.rawQuery("SELECT " + KEY_ID + "," + KEY_IMAGE + " FROM " + TABLE_CARS + " ORDER BY RANDOM() LIMIT 1", null);// make space after FROM and before ORDER BY

在您的getRandomImageKey（）方法中，并且在getCurrentCar（）方法中也做同样的事情

Answer 2

在您的DatabaseHandler类中，创建表语法错误。因此请更改此行

    db.execSQL("CREATE TABLE" + TABLE_CARS + ")" + KEY_ID + "INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_ADDRESS + " TEXT,"+  KEY_POSTCODE + " TEXT," + KEY_IMAGE  + " TEXT)");

进入

    db.execSQL("CREATE TABLE" + TABLE_CARS + "(" + KEY_ID + "INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_ADDRESS + " TEXT,"+  KEY_POSTCODE + " TEXT," + KEY_IMAGE  + " TEXT)");

正如弗兰克建议的那样，您的两个rawQuery语句是错误的，请在FROM后给空格

完成视力操作后，该Cursor将关闭。

Answer 3

不仅您的CREATE TABLE是错误的，而且其他人也正确指出了这一点（括号相反，并且缺少空格）：

db.execSQL("CREATE TABLE" + TABLE_CARS + ")" + KEY_ID + "INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_ADDRESS + " TEXT,"+  KEY_POSTCODE + " TEXT," + KEY_IMAGE  + " TEXT)");

应该

db.execSQL("CREATE TABLE " + TABLE_CARS + "(" + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," + KEY_ADDRESS + " TEXT,"+  KEY_POSTCODE + " TEXT," + KEY_IMAGE  + " TEXT)");

您还有另一个问题（缺少空格）：

Cursor cursor = db.rawQuery("SELECT * FROM" + TABLE_CARS, null);

应该

Cursor cursor = db.rawQuery("SELECT * FROM " + TABLE_CARS, null);

Answer 4

尝试使用此：

db.execSQL（“ CREATE TABLE” + TABLE_CARS +“（” + KEY_ID +“ INTEGER PRIMARY KEY AUTOINCREMENT，” + KEY_ADDRESS +“ TEXT，” + KEY_POSTCODE +“ TEXT，” + KEY_IMAGE +“ TEXT）”）；

Answer 5

尝试这个..

String createTableQuery=String.format(
                "CREATE TABLE %s(%s INTEGER PRIMARY KEY AUTOINCREMENT,%s TEXT,%s TEXT,%s TEXT)",
                TABLE_CARS, KEY_ID, KEY_ADDRESS, KEY_POSTCODE, KEY_IMAGE);

....

dB.execSQL(createTableQuery);