java 如何在android中为我的应用程序创建本地数据库
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How to create a local database in android for my application
提问by Shekhar
I want to create a simple database for my android application in sqlite. I just want to add my values to the table.
我想在 sqlite 中为我的 android 应用程序创建一个简单的数据库。我只想将我的值添加到表中。
This is my code but this is not working for me because the table is not shown at DDMS.
这是我的代码，但这对我不起作用，因为该表未显示在 DDMS 中。
public class QuickSubmitContext extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "submitManager";
private static final String TABLE_CONTACTS = "submit";
private static final String KEY_ID = "id";
private static final String KEY_PH_NO = "phone_number";
private static final String KEY_DNCA = "donotca";
private static final String KEY_CA = "callagain";
private static final String KEY_NOTE = "note";
public QuickSubmitContext(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS + "("
+ KEY_ID + " INTEGER PRIMARY KEY," + KEY_PH_NO + " TEXT,"
+ KEY_DNCA + " TEXT," + KEY_CA + " TEXT," + KEY_NOTE + " TEXT" + ")";
db.execSQL(CREATE_CONTACTS_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_CONTACTS);
// Create tables again
onCreate(db);
}
}
Logcat
逻辑猫
10-21 04:39:00.230: E/AndroidRuntime(835): FATAL EXCEPTION: main
10-21 04:39:00.230: E/AndroidRuntime(835): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.aspeage.quikw/com.aspeage.quikw.FragmentLayout}: java.lang.NullPointerException
10-21 04:39:00.230: E/AndroidRuntime(835): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
10-21 04:39:00.230: E/AndroidRuntime(835): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
10-21 04:39:00.230: E/AndroidRuntime(835): at android.app.ActivityThread.access0(ActivityThread.java:141)
10-21 04:39:00.230: E/AndroidRuntime(835): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
10-21 04:39:00.230: E/AndroidRuntime(835): at android.os.Handler.dispatchMessage(Handler.java:99)
10-21 04:39:00.230: E/AndroidRuntime(835): at android.os.Looper.loop(Looper.java:137)
10-21 04:39:00.230: E/AndroidRuntime(835): at android.app.ActivityThread.main(ActivityThread.java:5041)
10-21 04:39:00.230: E/AndroidRuntime(835): at java.lang.reflect.Method.invokeNative(Native Method)
10-21 04:39:00.230: E/AndroidRuntime(835): at java.lang.reflect.Method.invoke(Method.java:511)
10-21 04:39:00.230: E/AndroidRuntime(835): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
10-21 04:39:00.230: E/AndroidRuntime(835): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
10-21 04:39:00.230: E/AndroidRuntime(835): at dalvik.system.NativeStart.main(Native Method)
10-21 04:39:00.230: E/AndroidRuntime(835): Caused by: java.lang.NullPointerException
10-21 04:39:00.230: E/AndroidRuntime(835): at com.aspeage.quikw.FragmentLayout.onCreate(FragmentLayout.java:79)
10-21 04:39:00.230: E/AndroidRuntime(835): at android.app.Activity.performCreate(Activity.java:5104)
10-21 04:39:00.230: E/AndroidRuntime(835): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
10-21 04:39:00.230: E/AndroidRuntime(835): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
10-21 04:39:00.230: E/AndroidRuntime(835): ... 11 more
10-21 04:39:07.090: I/Process(835): Sending signal. PID: 835 SIG: 9
10-21 04:39:13.050: E/Trace(866): error opening trace file: No such file or directory (2)
回答by Stephen Lin
The recommended method to create a new SQLite database is to create a subclass of SQLiteOpenHelperand override the onCreate()method, in which you can execute a SQLite command to create tables in the database. For example:
创建新的SQLite数据库的推荐方法是创建一个子类SQLiteOpenHelper并覆盖该onCreate()方法，您可以在其中执行SQLite命令在数据库中创建表。例如：
public class DictionaryOpenHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 2;
private static final String DICTIONARY_TABLE_NAME = "dictionary";
private static final String DICTIONARY_TABLE_CREATE =
"CREATE TABLE " + DICTIONARY_TABLE_NAME + " (" +
KEY_WORD + " TEXT, " +
KEY_DEFINITION + " TEXT);";
DictionaryOpenHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(DICTIONARY_TABLE_CREATE);
}
}
Here are instructions. http://developer.android.com/guide/topics/data/data-storage.html#db
这是说明。 http://developer.android.com/guide/topics/data/data-storage.html#db
