我试图将此DBManager用作SQLite数据库帮助程序。问题是它确实创建了数据库但首先抛出了这个错误。我没有面对这个错误就得不到如何创建数据库。
注意：有类似问题但未解决此问题。它不会抛出写入外部存储权限异常。
这是我的数据库助手类：
public class DBManager extends SQLiteOpenHelper {
private static final String TAG = DBManager.class.getSimpleName();
// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "iap";
// Login table name
private static final String TABLE_STORIES = "stories";
private ArrayList<Story> storiesList = new ArrayList<>();
private Context mContext;
public DBManager(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
mContext = context;
}
// Creating Tables
@Override
public void onCreate(SQLiteDatabase db) {
if(checkDataBase()){
Log.d(TAG, "Database exists and readable");
}else {
String CREATE_LOGIN_TABLE = "CREATE TABLE " + TABLE_STORIES + "("
+ KEY_ID + " INTEGER PRIMARY KEY,"
+ KEY_TITLE + " TEXT,"
+ KEY_PIC + " TEXT,"
+ KEY_EXTERNAL_LINK + " TEXT,"
+ KEY_EXTERNAL_TITLE + " TEXT,"
+ KEY_PIC_CREDIT_LINK + " TEXT,"
+ KEY_PIC_CREDIT_TITLE + " TEXT,"
+ KEY_DATE + " TEXT)";
db.execSQL(CREATE_LOGIN_TABLE);
Log.d(TAG, "Database tables created");
}
}
/**
* Check if the database exist and can be read.
*
* @return true if it exists and can be read, false if it doesn't
*/
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
try {
checkDB = SQLiteDatabase.openDatabase(DATABASE_NAME, null,
SQLiteDatabase.OPEN_READONLY);
checkDB.close();
} catch (SQLiteException e) {
e.printStackTrace();
}
return checkDB != null;
/*File dbFile = mContext.getDatabasePath(DATABASE_NAME);
return dbFile.exists();*/
}
// Upgrading database
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older table if existed
db.execSQL("DROP TABLE IF EXISTS " + TABLE_STORIES);
// Create tables again
onCreate(db);
}
}
这是日志（查看最后一行）：
04-13 16:07:12.918 10920-10920/news.inapic.app E/SQLiteLog: (14) cannot open file at line 32456 of [bda77dda96]
04-13 16:07:12.918 10920-10920/news.inapic.app E/SQLiteLog: (14) os_unix.c:32456: (2) open(//iap) -
04-13 16:07:12.919 10920-10920/news.inapic.app E/SQLiteDatabase: Failed to open database 'iap'.
android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209)
at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193)
at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:808)
at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:793)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:696)
at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:671)
at news.inapic.app.Helpers.DBManager.checkDataBase(DBManager.java:82)
at news.inapic.app.Helpers.DBManager.onCreate(DBManager.java:53)
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:251)
at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:187)
at news.inapic.app.Helpers.DBManager.getStories(DBManager.java:139)
at news.inapic.app.Acitivity.MainActivity.setupViewPager(MainActivity.java:240)
at news.inapic.app.Acitivity.MainActivity.onCreate(MainActivity.java:209)
at android.app.Activity.performCreate(Activity.java:6679)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6119)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:808)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:793)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:696)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:671)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at news.inapic.app.Helpers.DBManager.checkDataBase(DBManager.java:82)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at news.inapic.app.Helpers.DBManager.onCreate(DBManager.java:53)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:251)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:187)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at news.inapic.app.Helpers.DBManager.getStories(DBManager.java:139)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at news.inapic.app.Acitivity.MainActivity.setupViewPager(MainActivity.java:240)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at news.inapic.app.Acitivity.MainActivity.onCreate(MainActivity.java:209)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.app.Activity.performCreate(Activity.java:6679)
04-13 16:07:12.919 10920-10920/news.inapic.app W/System.err: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
04-13 16:07:12.920 10920-10920/news.inapic.app W/System.err: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618)
04-13 16:07:12.920 10920-10920/news.inapic.app W/System.err: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)
04-13 16:07:12.920 10920-10920/news.inapic.app W/System.err: at android.app.ActivityThread.-wrap12(ActivityThread.java)
04-13 16:07:12.920 10920-10920/news.inapic.app W/System.err: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)
04-13 16:07:12.920 10920-10920/news.inapic.app W/System.err: at android.os.Handler.dispatchMessage(Handler.java:102)
04-13 16:07:12.920 10920-10920/news.inapic.app W/System.err: at android.os.Looper.loop(Looper.java:154)
04-13 16:07:12.920 10920-10920/news.inapic.app W/System.err: at android.app.ActivityThread.main(ActivityThread.java:6119)
04-13 16:07:12.920 10920-10920/news.inapic.app W/System.err: at java.lang.reflect.Method.invoke(Native Method)
04-13 16:07:12.920 10920-10920/news.inapic.app W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
04-13 16:07:12.920 10920-10920/news.inapic.app W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
04-13 16:07:12.921 10920-10920/news.inapic.app D/DBManager: Database tables created
答案 0 :(得分：1)
您可以创建一个静态实例方法来以单例类模式访问数据库。
public static DBManager instance;
/** Get instance of current database.*/
public static DBManager getInstance(Context context){
if(instace==null){
instance= new DBManager(context, DATABASE_NAME, null, DATABASE_VERSION);
}
return instace;
}
在创建时，您不需要检查数据库是否已打开。它会给你一个错误，因为你在创建之前尝试访问数据库。愿这对你有所帮助。
答案 1 :(得分：1)
无需检查onCreate()中是否存在数据库。你可以假设：
onConfigure()被称为此外，使用SQLiteOpenHelper