sqlite-Android中具有数据库故障的应用程序类

概述我在Android应用程序中无法访问SQLite数据库.我创建了一个包含SQLiteOpenHelper实例的应用程序类,但是,每当我尝试在另一个活动中打开数据库时,它就会崩溃.这是我的应用程序类：publicclassGlobalVariablesextendsApplication{privateLocationsDatalocations;p

我在Android应用程序中无法访问sqlite数据库.我创建了一个包含sqliteOpenHelper实例的应用程序类,但是,每当我尝试在另一个活动中打开数据库时,它就会崩溃.

这是我的应用程序类：

public class GlobalVariables extends Application {    private LocationsData locations;    public voID onCreate(Context context) {            locations = new LocationsData(context);    }    public LocationsData getLocations() {           return locations;    }}

这是我的sqliteOpenHelper类：

public class LocationsData extends sqliteOpenHelper{private static final String DATABASE_name = "locations.db";private static final int DATABASE_VERSION = 1;public static final String table_LOCATIONS = "locations";public static final String ColUMN_ID = "_ID";public static final String ColUMN_NICKname = "nickname";private static final String DATABASE_CREATE = "create table "        + table_LOCATIONS + "( " + ColUMN_ID        + " integer primary key autoincrement, " + ColUMN_NICKname        + " text not null);";public LocationsData(Context context) {    super(context, DATABASE_name, null, DATABASE_VERSION);}@OverrIDepublic voID onCreate(sqliteDatabase db) {    db.execsql(DATABASE_CREATE);}@OverrIDepublic voID onUpgrade(sqliteDatabase db, int oldVersion, int newVersion) {    db.execsql("DROP table IF EXISTS " + table_LOCATIONS);    onCreate(db);}

}

当我尝试在另一个活动中访问数据库时,出现错误：

    @OverrIDe    public voID onResume()    {         locationsData=((GlobalVariables)getApplication()).getLocations();         sqliteDatabase db = locationsData.getReadableDatabase();         super.onResume();    }

有什么帮助吗？谢谢！

Log Cat:05-10 02:00:50.146: D/AndroIDRuntime(532): Shutting down VM05-10 02:00:50.146: W/dalvikvm(532): threadID=1: thread exiting with uncaught exception (group=0x40015560)05-10 02:00:50.179: E/AndroIDRuntime(532): FATAL EXCEPTION: main05-10 02:00:50.179: E/AndroIDRuntime(532): java.lang.RuntimeException: Unable to resume activity {com.John.seniorDesign/com.John.seniorDesign.Locationstabactivity}: java.lang.NullPointerException05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.app.ActivityThread.performResumeActivity(ActivityThread.java:2120)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.app.LocalActivityManager.movetoState(LocalActivityManager.java:138)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.app.LocalActivityManager.startActivity(LocalActivityManager.java:339)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.Widget.TabHost$IntentContentStrategy.getContentVIEw(TabHost.java:654)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.Widget.TabHost.setCurrentTab(TabHost.java:326)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.Widget.TabHost.onTabSelectionChanged(TabHost.java:132)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.Widget.TabWidget$TabClickListener.onClick(TabWidget.java:456)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.vIEw.VIEw.performClick(VIEw.java:2485)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.vIEw.VIEw$PerformClick.run(VIEw.java:9080)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.os.Handler.handleCallback(Handler.java:587)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.os.Handler.dispatchMessage(Handler.java:92)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.os.Looper.loop(Looper.java:130)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.app.ActivityThread.main(ActivityThread.java:3683)05-10 02:00:50.179: E/AndroIDRuntime(532):  at java.lang.reflect.Method.invokeNative(Native Method)05-10 02:00:50.179: E/AndroIDRuntime(532):  at java.lang.reflect.Method.invoke(Method.java:507)05-10 02:00:50.179: E/AndroIDRuntime(532):  at com.androID.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)05-10 02:00:50.179: E/AndroIDRuntime(532):  at com.androID.internal.os.ZygoteInit.main(ZygoteInit.java:597)05-10 02:00:50.179: E/AndroIDRuntime(532):  at dalvik.system.NativeStart.main(Native Method)05-10 02:00:50.179: E/AndroIDRuntime(532): Caused by: java.lang.NullPointerException05-10 02:00:50.179: E/AndroIDRuntime(532):  at com.John.seniorDesign.Locationstabactivity.onResume(Locationstabactivity.java:75)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.app.Instrumentation.callActivityOnResume(Instrumentation.java:1150)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.app.Activity.performResume(Activity.java:3832)05-10 02:00:50.179: E/AndroIDRuntime(532):  at androID.app.ActivityThread.performResumeActivity(ActivityThread.java:2110)05-10 02:00:50.179: E/AndroIDRuntime(532):  ... 17 more

解决方法:

在GlobalVariables中,将上下文更改为新的LocationsData中的getApplicationContext()并从onCreate中删除上下文-此签名不存在.

编辑：

public class GlobalVariables extends Application {    private LocationsData locations;    @OverrIDe    public voID onCreate() {            locations = new LocationsData(getApplicationContext());    }    public LocationsData getLocations() {           return locations;    }}

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