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垂直布局，高度无法充满怎么解决 - App Inventor 2 中文网 - 清泛IT社区，为创新赋能！
C:\Users\Lenovo\Desktop\wechat_2025-04-06_205731_542.png你好，请把 Screen1 下面的组件树展开看看。
目测是因为这个 垂直布局 的父组件，高度没有充满整个屏幕，所以它只能充满它的父组件的高度。没有设置的选项App Inventor 2 发表...
Adding a column to an existing table in a Rails migration
...enerate a new migration (rails generate migration add_email_to_users email:string will do the trick).
It will create a migration file containing line:
add_column :users, email, string
Then do a rake db:migrate and it'll run the new migration, creating the new column.
If you have not yet run the ori...
registerForRemoteNotificationTypes: is not supported in iOS 8.0 and later
... Xcode 6, then you will need to use conditional compiling as follows:
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000
if ([application respondsToSelector:@selector(registerUserNotificationSettings:)]) {
// use registerUserNotificationSettings
} else {
// use registerForRemoteNotificationTyp...
How to install a specific version of a ruby gem?
Using the command-line gem tool, how can I install a specific version of a gem?
6 Answers
...
Is there a “null coalescing” operator in JavaScript?
... coalescing operator (??) is using a logical OR (||):
var whatIWant = someString || "Cookies!";
There are cases (clarified below) that the behaviour won't match that of C#, but this is the general, terse way of assigning default/alternative values in JavaScript.
Clarification
Regardless of th...
How to bundle a native library and a JNI library inside a JAR?
...m.load(File) to load the library instead of the typical System.loadLibrary(String) which searches the java.library.path system property. This method makes installation much simpler as the user does not have to install the JNI library on his system, at the expense, however, that all platforms might n...
Does Spring Data JPA have any way to count entites using method name resolving?
...ository extends CrudRepository<User, Integer> {
Long countByName(String name);
}
2) The old way, Using @Query annotation.
Example,
public interface UserRepository extends CrudRepository<User, Integer> {
@Query("SELECT COUNT(u) FROM User u WHERE u.name=?1")
Long aMethodNa...
Generic method multiple (OR) type constraint
... You can, however, define overloads for specific types:
public void test(string a, string arg);
public void test(string a, Exception arg);
If those are part of a generic class, they will be preferred over the generic version of the method.
...
Is there a JavaScript / jQuery DOM change listener?
Essentially I want to have a script execute when the contents of a DIV change. Since the scripts are separate (content script in the Chrome extension & webpage script), I need a way simply observe changes in DOM state. I could set up polling but that seems sloppy.
...
Most efficient way to store thousand telephone numbers
...
In what follows, I treat the numbers as integer variables (as opposed to strings):
Sort the numbers.
Split each number into the first five digits and the last five digits.
The first five digits are the same across numbers, so store them just once. This will require 17 bits of storage.
Store the ...