java - 创建数据库时未在 Android 中创建 SQLite 数据库表

Question

我正在努力创建一个 Android 应用程序。我是 Android 和 Java 应用程序开发的初学者，但我有丰富的 Web 开发经验。

我正在尝试创建一个数据库，然后在 SQLite 中创建我的第一个表。它正在创建数据库而不是数据库表。

我已经创建了 Contaract 类。

package com.haafiz.project;

import android.provider.BaseColumns;

public final class ProjectContaract {

    public ProjectContaract(){}

    public static abstract class Site implements BaseColumns{
        public static final String TABLE_NAME = "site";
        public static final String COLUMN_NAME_SITE_NAME = "site_name";
        public static final String COLUMN_NAME_LOGIN = "login_name";
        public static final String COLUMN_NAME_HOST = "host";
        public static final String COLUMN_NAME_PASSWORD = "password";
    }
}

然后是数据库助手类。

package com.haafiz.project;

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


public class DBHelper extends SQLiteOpenHelper {

    private static final String TEXT_TYPE = " TEXT";
    private static final String COMMA_SEP = ",";
    private static final String SQL_CREATE_ENTRIES =
            "CREATE TABLE " + ProjectContaract.Site.TABLE_NAME + " (" +
                    projectContaract.Site._ID + " INTEGER PRIMARY KEY," +
                    projectContaract.Site.COLUMN_NAME_SITE_NAME + TEXT_TYPE + COMMA_SEP +
                    projectContaract.Site.COLUMN_NAME_LOGIN + TEXT_TYPE + COMMA_SEP +
                    projectContaract.Site.COLUMN_NAME_HOST + TEXT_TYPE + COMMA_SEP +
                    projectContaract.Site.COLUMN_NAME_PASSWORD + TEXT_TYPE + " )";

    private static final String SQL_DELETE_ENTRIES =
            "DROP TABLE IF EXISTS " + ProjectContaract.Site.TABLE_NAME;

    public static final int DATABASE_VERSION = 1;
    public static final String DATABASE_NAME = "Project";

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

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(SQL_CREATE_ENTRIES);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
        db.execSQL(SQL_DELETE_ENTRIES);
        onCreate(db);
    }

    @Override
    public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        onUpgrade(db, oldVersion, newVersion);
    }
}

这里是我使用 DB Helper 的主要 Activity ，如下所示:

package com.haafiz.project;

import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;


public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        projectDBHelper dbHelper = new projectDBHelper(getApplicationContext());

        // Gets the data repository in read mode
        SQLiteDatabase db = dbHelper.getWritableDatabase();

        // Projection that specifies which columns from the database
        String[] projection = {
                projectContaract.Site._ID,
                projectContaract.Site.COLUMN_NAME_SITE_NAME,
                projectContaract.Site.COLUMN_NAME_LOGIN,
                projectContaract.Site.COLUMN_NAME_HOST,
                projectContaract.Site.COLUMN_NAME_PASSWORD
        };

        // How you want the results sorted in the resulting Cursor
        String sortOrder =
                projectContaract.Site.COLUMN_NAME_SITE_NAME + " DESC";

        Cursor c = db.query(
                projectContaract.Site.TABLE_NAME,  // The table to query
                projection,                               // The columns to return
                null,                                // The columns for the WHERE clause
                null,                            // The values for the WHERE clause
                null,                                     // don't group the rows
                null,                                     // don't filter by row groups
                sortOrder                                 // The sort order
        );

        setContentView(R.layout.activity_main);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

正在创建数据库，但没有创建表，我使用带有模拟器的 adb shell attach 进行检查。我究竟做错了什么？未创建表。

重要的是我没有在日志中收到与此相关的错误。

但是在以前“仅显示选定的应用程序”的下拉列表中带有“无过滤器”的 logcat 中，并且在过滤器搜索框中带有“sql”，它在日志 cat 中显示以下消息:

    08-04 00:41:35.494      403-474/android.process.media V/MediaScanner﹕ pruneDeadThumbnailFiles... android.database.sqlite.SQLiteCursor@41302da8
08-04 00:41:35.494      403-474/android.process.media V/MediaScanner﹕ /pruneDeadThumbnailFiles... android.database.sqlite.SQLiteCursor@41302da8
08-04 00:54:02.685      623-632/com.haafiz.project E/SQLiteDatabase﹕ close() was never explicitly called on database '/data/data/com.haafiz.project/databases/project'
    android.database.sqlite.DatabaseObjectNotClosedException: Application did not close the cursor or database object that was opened here
            at android.database.sqlite.SQLiteDatabase.<init>(SQLiteDatabase.java:1943)
            at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:1007)
            at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:986)
            at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:1051)
            at android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:770)
            at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:221)
            at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:157)
            at com.haafiz.project.MainActivity.onCreate(MainActivity.java:20)
            at android.app.Activity.performCreate(Activity.java:4466)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
            at android.app.ActivityThread.access$600(ActivityThread.java:123)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4424)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
            at dalvik.system.NativeStart.main(Native Method)
08-04 00:54:02.766      623-632/com.haafiz.project E/System﹕ java.lang.IllegalStateException: Don't have database lock!
            at android.database.sqlite.SQLiteDatabase.verifyLockOwner(SQLiteDatabase.java:2090)
            at android.database.sqlite.SQLiteDatabase$1.entryRemoved(SQLiteDatabase.java:2182)
            at android.database.sqlite.SQLiteDatabase$1.entryRemoved(SQLiteDatabase.java:2178)
            at android.util.LruCache.trimToSize(LruCache.java:197)
            at android.util.LruCache.evictAll(LruCache.java:285)
            at android.database.sqlite.SQLiteDatabase.deallocCachedSqlStatements(SQLiteDatabase.java:2143)
            at android.database.sqlite.SQLiteDatabase.closeClosable(SQLiteDatabase.java:1126)
            at android.database.sqlite.SQLiteDatabase.finalize(SQLiteDatabase.java:1914)
            at java.lang.Daemons$FinalizerDaemon.doFinalize(Daemons.java:182)
            at java.lang.Daemons$FinalizerDaemon.run(Daemons.java:168)
            at java.lang.Thread.run(Thread.java:856)

除了前两行，log cat 输出的其他行，所有其他行都以红色突出显示。

Answer 1

似乎数据库没有正确关闭。有时，当您经常重新安装应用程序的构建时，这可能会在开发过程中发生。

卸载应用程序并重新安装。或者打开“设置”>“应用”>“[您的应用]”，然后点击“清除数据”按钮。其中任何一个都将删除现有的数据库文件，因此下次尝试打开它时将创建一个新文件。