Android SQLite 应用程序崩溃

Question

我一直在关注 TheNewBoston 的初学者 Android 应用程序开发教程。我目前在 SQLite 部分。我完全复制了他在教程中输入的所有内容。不幸的是，教程中的代码有效，而我的代码无效，我不明白为什么。我需要帮助。这是我输入的内容:

主要 Activity .java:

    package com.example.sha_elregencia.database;

import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.Cursor;
import android.content.Context;
import android.content.ContentValues;

public class MyDBHandler extends SQLiteOpenHelper{

    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "products.db"; //name of file
    public static final String TABLE_PRODUCTS = "products"; //name of table
    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_PRODUCTNAME = "productname";

    public MyDBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, DATABASE_NAME, factory, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        String query = "CREATE TABLE " + TABLE_PRODUCTS + "(" +
                COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT " +
                COLUMN_PRODUCTNAME + " TEXT " +
                ");";
        db.execSQL(query);
    }

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

    public void addProduct(Products product) {
        ContentValues values = new ContentValues();
        values.put(COLUMN_PRODUCTNAME, product.get_productname());
        SQLiteDatabase db = getWritableDatabase();
        db.insert(TABLE_PRODUCTS, null, values);
        db.close();
    }

    public void deleteProduct(String productName) {
        SQLiteDatabase db = getWritableDatabase();
        db.execSQL("DELETE FROM " + TABLE_PRODUCTS + " WHERE " + COLUMN_PRODUCTNAME + "=\"" + productName + "\";");
                                                                                            //must be the variable passed in
    }

    public String databaseToString() {
        String dbString = "";
        SQLiteDatabase db = getWritableDatabase();
        String query = "SELECT * FROM  " + TABLE_PRODUCTS + " WHERE 1 ";
                            //means select                          //select every row
                            //everything

        //Cursor points to a location in your results
        Cursor c = db.rawQuery(query, null);
        c.moveToFirst();

        while(!c.isAfterLast()) {
            if(c.getString(c.getColumnIndex("productname")) != null) {
                dbString += c.getString(c.getColumnIndex("productname"));
                dbString += "\n";
            }
            c.moveToNext();
        }
        db.close();
        return dbString;
    }
}

产品.java:

package com.example.sha_elregencia.database;

public class Products {

    private int _id;
    private String _productname;

    public Products() {
    }

    public Products(String productname) {
        this._productname = productname;
    }

    public void set_id(int _id) {
        this._id = _id;
    }

    public void set_productname(String _productname) {
        this._productname = _productname;
    }

    public int get_id() {
        return _id;
    }

    public String get_productname() {
        return _productname;
    }
}

MyDBHandler.java:

package com.example.sha_elregencia.database;

import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.Cursor;
import android.content.Context;
import android.content.ContentValues;

public class MyDBHandler extends SQLiteOpenHelper{

    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "products.db"; //name of file
    public static final String TABLE_PRODUCTS = "products"; //name of table
    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_PRODUCTNAME = "productname";

    public MyDBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
        super(context, DATABASE_NAME, factory, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        String query = "CREATE TABLE " + TABLE_PRODUCTS + "(" +
                COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT " +
                COLUMN_PRODUCTNAME + " TEXT " +
                ");";
        db.execSQL(query);
    }

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

    public void addProduct(Products product) {
        ContentValues values = new ContentValues();
        values.put(COLUMN_PRODUCTNAME, product.get_productname());
        SQLiteDatabase db = getWritableDatabase();
        db.insert(TABLE_PRODUCTS, null, values);
        db.close();
    }

    public void deleteProduct(String productName) {
        SQLiteDatabase db = getWritableDatabase();
        db.execSQL("DELETE FROM " + TABLE_PRODUCTS + " WHERE " + COLUMN_PRODUCTNAME + "=\"" + productName + "\";");
                                                                                            //must be the variable passed in
    }

    public String databaseToString() {
        String dbString = "";
        SQLiteDatabase db = getWritableDatabase();
        String query = "SELECT * FROM  " + TABLE_PRODUCTS + " WHERE 1 ";
                            //means select                          //select every row
                            //everything

        //Cursor points to a location in your results
        Cursor c = db.rawQuery(query, null);
        c.moveToFirst();

        while(!c.isAfterLast()) {
            if(c.getString(c.getColumnIndex("productname")) != null) {
                dbString += c.getString(c.getColumnIndex("productname"));
                dbString += "\n";
            }
            c.moveToNext();
        }
        db.close();
        return dbString;
    }
}

每次我运行它时，它都会崩溃并提示:

08-11 15:26:10.791    9068-9068/? I/art﹕ Not late-enabling -Xcheck:jni (already on)
08-11 15:26:10.983    9068-9068/com.example.sha_elregencia.database E/SQLiteLog﹕ (1) near "productname": syntax error
08-11 15:26:10.984    9068-9068/com.example.sha_elregencia.database D/AndroidRuntime﹕ Shutting down VM
08-11 15:26:10.984    9068-9068/com.example.sha_elregencia.database E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.sha_elregencia.database, PID: 9068
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sha_elregencia.database/com.example.sha_elregencia.database.MainActivity}: android.database.sqlite.SQLiteException: near "productname": syntax error (code 1): , while compiling: CREATE TABLE products(_id INTEGER PRIMARY KEY AUTOINCREMENT productname TEXT );
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: android.database.sqlite.SQLiteException: near "productname": syntax error (code 1): , while compiling: CREATE TABLE products(_id INTEGER PRIMARY KEY AUTOINCREMENT productname TEXT );
            at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
            at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
            at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
            at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
            at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
            at android.database.sqlite.SQLiteStatement.<init>(SQLiteStatement.java:31)
            at android.database.sqlite.SQLiteDatabase.executeSql(SQLiteDatabase.java:1674)
            at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1605)
            at com.example.sha_elregencia.database.MyDBHandler.onCreate(MyDBHandler.java:28)
            at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:251)
            at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163)
            at com.example.sha_elregencia.database.MyDBHandler.databaseToString(MyDBHandler.java:53)
            at com.example.sha_elregencia.database.MainActivity.printDatabase(MainActivity.java:40)
            at com.example.sha_elregencia.database.MainActivity.onCreate(MainActivity.java:24)
            at android.app.Activity.performCreate(Activity.java:5990)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

感谢您提供的任何帮助

Answer 1

您只是缺少一个,。

String query = "CREATE TABLE " + TABLE_PRODUCTS + "(" +
                COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT ," +
                COLUMN_PRODUCTNAME + " TEXT " +
                ");";