Tutorial by Examples: define

When we create a button in layout, we can use the android:onClick attribute to reference a method in code to handle clicks. Button <Button android:width="120dp" android:height="wrap_content" android:text="Click me" android:onClick="handleCl...

Strings are typically stored in the resource file strings.xml. They are defined using a <string> XML element. The purpose of strings.xml is to allow internationalisation. You can define a strings.xml for each language iso code. Thus when the system looks for the string 'app_name' it first che...

In order to define a string array write in a resources file res/values/filename.xml <string-array name="string_array_name"> <item>text_string</item> <item>@string/string_id</item> </string-array> for example res/values/arrays.xml <?x...

Dimensions are typically stored in a resource file names dimens.xml. They are defined using a <dimen> element. res/values/dimens.xml <?xml version="1.0" encoding="utf-8"?> <resources> <dimen name="small_padding">5dp</dimen> &l...

Integers are typically stored in a resource file named integers.xml, but the file name can be chosen arbitrarily. Each integer is defined by using an <integer> element, as shown in the following file: res/values/integers.xml <?xml version="1.0" encoding="utf-8"?> &...

In order to define an integer array write in a resources file res/values/filename.xml <integer-array name="integer_array_name"> <item>integer_value</item> <item>@integer/integer_id</item> </integer-array> for example res/values/arrays.xm...

Colors are usually stored in a resource file named colors.xml in the /res/values/ folder. They are defined by <color> elements: <?xml version="1.0" encoding="utf-8"?> <resources> <color name="colorPrimary">#3F51B5</color> <c...

The differences between null and undefined null and undefined share abstract equality == but not strict equality ===, null == undefined // true null === undefined // false They represent slightly different things: undefined represents the absence of a value, such as before an identifier/...

5 It allows us to define a property in an existing object using a property descriptor. var obj = { }; Object.defineProperty(obj, 'foo', { value: 'foo' }); console.log(obj.foo); Console output foo Object.defineProperty can be called with the following options: Object.definePropert...

At first glance it may appear that null and undefined are basically the same, however there are subtle but important differences. undefined is the absence of a value in the compiler, because where it should be a value, there hasn't been put one, like the case of an unassigned variable. undefined...

BuildConfigField Gradle allows buildConfigField lines to define constants. These constants will be accessible at runtime as static fields of the BuildConfig class. This can be used to create flavors by defining all fields within the defaultConfig block, then overriding them for individual build fla...

class Animal def method_missing(method, *args, &block) "Cannot call #{method} on Animal" end end => Animal.new.say_moo > "Cannot call say_moo on Animal"

Avoid destructive operations on quoted objects. Quoted objects are literal objects. They are possibly embedded in the code in some way. How this works and the effects of modifications are unspecified in the Common Lisp standard, but it can have unwanted consequences like modifying shared data, tryin...

Define a menu in res/menu <?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto"> <item android:id="@+id/first_...

Predefined macros are those that the compiler defines (in contrast to those user defines in the source file). Those macros must not be re-defined or undefined by user. The following macros are predefined by the C++ standard: __LINE__ contains the line number of the line this macro is used on, an...

By default, Interface Builder doesn't accept the CGColor datatype, so to allow adding a CGColor using user defined attributes in interface builder; one may want to use an extension like this: Swift Extension : extension CALayer { func borderUIColor() -> UIColor? { return borderCol...

Letters 3.0 let letters = CharacterSet.letters let phrase = "Test case" let range = phrase.rangeOfCharacter(from: letters) // range will be nil if no letters is found if let test = range { print("letters found") } else { print("letters not found") }...

Simple check To check if constant is defined use the defined function. Note that this function doesn't care about constant's value, it only cares if the constant exists or not. Even if the value of the constant is null or false the function will still return true. <?php define("GOOD&quo...

A predefined macro is a macro that is already understood by the C pre processor without the program needing to define it. Examples include Mandatory Pre-Defined Macros __FILE__, which gives the file name of the current source file (a string literal), __LINE__ for the current line number (an int...

The typical example is an abstract shape class, that can then be derived into squares, circles, and other concrete shapes. The parent class: Let's start with the polymorphic class: class Shape { public: virtual ~Shape() = default; virtual double get_surface() const = 0; virtual vo...