Question

Hi是从Playstore执行更新时扩展Application Called的类。我的问题是我在我的Application Class的onCreate函数上初始化了SQLiteDatabase。当我这样做并升级我的应用程序崩溃时出现以下错误

java.lang.NullPointerException：尝试调用虚方法＆＃39; boolean android.database.sqlite.SQLiteDatabase.isOpen（）

这意味着SQLiteDatabase未在UPDATE初始化。

任何想法???

下面我们更多

java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.database.sqlite.SQLiteDatabase.isOpen()' on a null object reference
at com.cellulant.consumerapp.db.DBAdapter.getSqliteDatabase(DBAdapter.java:518)
at com.cellulant.consumerapp.fragments.PaymentsFragment.onCreateView(PaymentsFragment.java:113)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2074)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1286)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:758)
at android.support.v4.app.FragmentManagerImpl.execSingleAction(FragmentManager.java:1632)
at android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss(BackStackRecord.java:637)
at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:143)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1235)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1083)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1609)
at android.view.View.measure(View.java:17923)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5698)
at android.support.design.widget.CoordinatorLayout.onMeasureChild(CoordinatorLayout.java:668)
at android.support.design.widget.CoordinatorLayout.onMeasure(CoordinatorLayout.java:735)
at android.view.View.measure(View.java:17923)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5698)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:465)
at android.view.View.measure(View.java:17923)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:1079)
at android.view.View.measure(View.java:17923)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5698)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:465)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
at android.view.View.measure(View.java:17923)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5698)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1692)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:760)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:629)
at android.view.View.measure(View.java:17923)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5698)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:465)
at android.view.View.measure(View.java:17923)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5698)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1692)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:760)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:629)
at android.view.View.measure(View.java:17923)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5698)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:465)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2733)
at android.view.View.measure(View.java:17923)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2461)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1463)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1687)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1341)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6700)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:800)
at android.view.Choreographer.doCallbacks(Choreographer.java:603)
at android.view.Choreographer.doFrame(Choreographer.java:572)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:786)
at android.os.Handler.handleCallback(Handler.java:815)
at android.os.Handler.dispatchMessage(Handler.java:104)
at android.os.Looper.loop(Looper.java:194)
at android.app.ActivityThread.main(ActivityThread.java:5637)
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:959)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)

DB Apdater

public class DBAdapter扩展了SQLHelper {

private CustomerTable customerTable;
private ProfilesTable profilesTable;


/**
 * @param context   Application Context
 * @param dbName    Database name
 * @param dbVersion database version
 */
public DBAdapter(Context context, final String dbName, final int dbVersion) {

    super(context, dbName, null, dbVersion);
    customerTable = new CustomerTable();
    billsTable = new BillsTable();

}

/***
 * Create individual table needed in database
 *
 * @param sqlDB Database
 */
private void createInitialTables(SQLiteDatabase sqlDB) {

    try {
        customerTable.createTable(sqlDB);
        billsTable.createTable(sqlDB);


    } catch (Exception e) {
        LogUtils.showException(e);
    }


}
@Override
public void onCreate(SQLiteDatabase sqlDB) {
    createInitialTables(sqlDB);
    super.onCreate(sqlDB);
}

@Override
public void onOpen(SQLiteDatabase db) {
    super.onOpen(db);
}

/**
 * This method is responsible for closing the database connection.
 *
 * @param db Database
 */
public void close(SQLiteDatabase db) {
    super.close();
    //Check if there is any open connection before closing.
    if (db.isOpen()) {
        db.close();
    }
}


@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    super.onUpgrade(db, oldVersion, newVersion);


    if (oldVersion < 21) {


        boolean tableSMSTemplateColumnIsDefault = StringUtils.checkIfColumnExists(db, SMSTemplateTable.class.getSimpleName(), SMSTemplateMap.PARSE_TYPE);
        if (!tableSMSTemplateColumnIsDefault) {
            db.execSQL(ALTER_SMS_TEMPLATES_PARSE_TYPE);
        }
        boolean tableMerchantColumnIsDefault = StringUtils.checkIfColumnExists(db, MerchantPayersTable.class.getSimpleName(), MerchantPayersMap.IS_DEFAULT);
        if (!tableMerchantColumnIsDefault) {
            db.execSQL(ALTER_MERCHANT_PAYER_IS_DEFAULT);
        }



    }

}

@Override
public SQLiteDatabase getSqliteDatabase() {
    if (!super.getSQLiteDatabase().isOpen()) {
        open();
    }
    return super.getSQLiteDatabase();
}

/*
 * Getter Methods
 */

public CustomerTable getCustomerTable() {
    return customerTable;
}

public ProfilesTable getProfilesTable() {
    return profilesTable;
}

}

Answer 1

Android应用程序升级是否会调用扩展应用程序的类？

不直接。应用程序升级将终止您的进程。创建进程的新实例时，将创建Application子类的新实例。完全当创建流程的新实例时会有所不同，具体取决于应用设置，用户正在做什么等等。

请记住，在创建流程时，您的任何活动都可能是用户的起点。用户频繁将从您的启动器活动开始，但情况并非总是如此。

例如，假设您的启动器活动是活动A，它会打开活动B，从而打开活动C.此时，用户获得可用更新的Notification。因此，用户点击Notification，转到Play商店（或任何地方），并请求更新应用。您的流程将在此过程中终止。升级完成后，用户将返回到您的应用程序（主屏幕启动器图标，概览/最近任务列表等）。此时，您将获得一个新进程...并且将创建活动C并将其带到前台。如果您的代码假定用户将始终通过活动A，则可能会遇到问题。

这不是应用升级所特有的。用户可能已经离开A-> B-＆gt; C，按下HOME，进入另一个应用程序10分钟，然后返回到您的应用程序。当您的UI处于后台时，您的进程可能已被终止，只是为了释放系统RAM。再一次，当用户返回您的应用程序时，您将获得一个新进程，用户将看到活动C，而不是活动A.

Android应用程序升级是否会调用扩展应用程序的类？

1 个答案: