What is r java class in android

Understand the R Class in Android

R.java is the dynamically generated class, created during build process to dynamically identify all assets (from strings to android widgets to layouts), for usage in java classes in Android app. Note this R.java is Android specific (though you may be able to duplicate it for other platforms, its very convenient), so it doesn’t have much to do with Java language constructs. Take a look here, for more details.

What is R class in android

Your question is duplicate of Understand the R class in Android

When your application is compiled, aapt generates the R class, which
contains resource IDs for all the resources in your res/ directory.
For each type of resource, there is an R subclass (for example,
R.drawable for all drawable resources) and for each resource of that
type, there is a static integer (for example, R.drawable.icon). This
integer is the resource ID that you can use to retrieve your resource.

I got this detail from the below link ,check this once for more details :
http://developer.android.com/guide/topics/resources/accessing-resources.html

What is the class R in Android?

R is a class containing the definitions for all resources of a particular application package. It is in the namespace of the application package.

For example, if you say in your manifest your package name is com.foo.bar , an R class is generated with the symbols of all your resources in com.foo.bar.R .

There are generally two R classes you will deal with

It is named R because that stands for Resources, and there is no point in making people type something longer, especially since it is common to end up with fairly long symbol names after it, that can cause a fair amount of line wrapper.

Android studio hides R class

You can find R class by searching it with «shift + cmd + o» or «double shift».

I guess new android studio update directs to the xml source of the resource.

What does R.id.myView refer to?

R — R.java is an auto-generated file by aapt (Android Asset Packaging Tool) which contains resource IDs for all the resources of res directory.

public final class R 
extends Object

.id — Find view using its id «defined by you»

public static final class R.id 
extends Object

myView — It is the view that you defined using the android:id=»@+id/your_view» attribute in your XML file.

So, finally we can find or identify any view using R.id.your_view.

Meaning of R.layout.activity_main in android development (JAVA language)

R.java is a class (with inner classes, like layout or string ) generated during the build process with references to your app’s resources. Every resource you create (or which is provided by Android) is referenced by an integer in R , called a resource id.

R.layout.* references any layout resource you have created, usually in /res/layout . So if you created an activity layout called activity_main.xml , you can then use the reference in R.layout.activity_main to access it. Many built-in functionality readily accepts such a resource id, for example setContentView(int layoutResid) which you use during the creation of your activity and where you probably encountered this particular example.

If you create a string resource (in strings.xml) like this:

it will get a new reference in R.string.app_name . You can then use this everywhere where a string resource is accepted, for example the android:label for your application in AndroidManifest.xml , or on a TextView; either in the xml:

 android:layout_width="wrap_content" 
android:layout_height="wrap_content" 
android:text="@string/app_name" 
/>

or in code: textview.setText(R.string.app_name) .

You can access resources programmatically using the Resources class, to which you can get a reference by calling getResources on any context (like your activity). So for example you can get your app name described above in your activity by calling this.getResources().getString(R.string.app_name) .

You can also supply different resources for different device properties/settings (like screen size or language), which you can access using the same references in R . The easiest example here, imho, is strings: if you add a new values folder in /res with a language specifier (so /res/values-nl for Dutch) and you add strings with the same identifier but a different translation and the resource management system cleverly figures out which one to provide for you based on your user’s device.

I hope this helps a bit. For more information on resources see the documentation.

the R.java file in android studio 3.4

\app\build\generated\not_namespaced_r_class_sources\debug\processDebugResources\r\\R.java

package_name_tree means : If package is a.b.c
the goto: /a/b/c/R.java

Why I do not need to import the android R class?

It is because your MainActivity.java are inside the package name which is the same as package name declared in AndroidManifest.xml :

package=»tld.mydomain.buttonclickcounter»>

The R.java will be generated based on the package name in AndroidManifest.xml . So, if you’re using other package name like tld.mydomain :

you then need to import the R.java with tld.mydomain.R .

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What is r java class in android

Android R .java is a class that contain definitions for all the resources a specific application that you are building. Every resource that is used in you application will have its id in the android r .java file.

Android R with example:

Suppose you drag a simple plain text view into the main screen of your main-activity.xml now this plain text view will have its resource id in the android R.java file. In the same if you look at the coding given below you will see resource ids for different components, such as icon, texts, themes etc.

This class contain two types of members:

• R.java file is automatically generated by aapt(Android Asset Packaging Tool).
• User is not supposed to change this; you change this it will be erased as it is auto generated every time.

Android R.java Path: /gen/com/foo/R.java

What if you delete the R.java file ?

Andorid R.java Code:

/* AUTO-GENERATED FILE. DO NOT MODIFY. * * This class was automatically generated by the * aapt tool from the resource data it found. It * should not be modified by hand. */ package com.lasttry; public final class R < public static final class attr < >public static final class dimen < /** Default screen margins, per the Android Design guidelines. Customize dimensions originally defined in res/values/dimens.xml (such as screen margins) for sw720dp devices (e.g. 10" tablets) in landscape here. */ public static final int activity_horizontal_margin=0x7f040000; public static final int activity_vertical_margin=0x7f040001; >public static final class drawable < public static final int ic_launcher=0x7f020000; >public static final class id < public static final int action_settings=0x7f080001; public static final int result=0x7f080000; >public static final class layout < public static final int activity_main=0x7f030000; >public static final class menu < public static final int main=0x7f070000; >public static final class string < public static final int action_settings=0x7f050001; public static final int app_name=0x7f050000; public static final int hello_world=0x7f050002; >public static final class style < /** Base application theme, dependent on API level. This theme is replaced by AppBaseTheme from res/values-vXX/styles.xml on newer devices. Theme customizations available in newer API levels can go in res/values-vXX/styles.xml, while customizations related to backward-compatibility can go here. Base application theme for API 11+. This theme completely replaces AppBaseTheme from res/values/styles.xml on API 11+ devices. API 11 theme customizations can go here. Base application theme for API 14+. This theme completely replaces AppBaseTheme from BOTH res/values/styles.xml and res/values-v11/styles.xml on API 14+ devices. API 14 theme customizations can go here. */ public static final int AppBaseTheme=0x7f060000; /** Application theme. All customizations that are NOT specific to a particular API-level can go here. */ public static final int AppTheme=0x7f060001; >>

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Understand the R Class in Android

R.java is the dynamically generated class, created during build process to dynamically identify all assets (from strings to android widgets to layouts), for usage in java classes in Android app. Note this R.java is Android specific (though you may be able to duplicate it for other platforms, its very convenient), so it doesn’t have much to do with Java language constructs. Take a look here, for more details.

What is R class in android

Your question is duplicate of Understand the R class in Android

When your application is compiled, aapt generates the R class, which
contains resource IDs for all the resources in your res/ directory.
For each type of resource, there is an R subclass (for example,
R.drawable for all drawable resources) and for each resource of that
type, there is a static integer (for example, R.drawable.icon). This
integer is the resource ID that you can use to retrieve your resource.

I got this detail from the below link ,check this once for more details :
http://developer.android.com/guide/topics/resources/accessing-resources.html

What is the class R in Android?

R is a class containing the definitions for all resources of a particular application package. It is in the namespace of the application package.

For example, if you say in your manifest your package name is com.foo.bar , an R class is generated with the symbols of all your resources in com.foo.bar.R .

There are generally two R classes you will deal with

It is named R because that stands for Resources, and there is no point in making people type something longer, especially since it is common to end up with fairly long symbol names after it, that can cause a fair amount of line wrapper.

Android studio hides R class

You can find R class by searching it with «shift + cmd + o» or «double shift».

I guess new android studio update directs to the xml source of the resource.

What does R.id.myView refer to?

R — R.java is an auto-generated file by aapt (Android Asset Packaging Tool) which contains resource IDs for all the resources of res directory.

public final class R 
extends Object

.id — Find view using its id «defined by you»

public static final class R.id 
extends Object

myView — It is the view that you defined using the android:id=»@+id/your_view» attribute in your XML file.

So, finally we can find or identify any view using R.id.your_view.

Meaning of R.layout.activity_main in android development (JAVA language)

R.java is a class (with inner classes, like layout or string ) generated during the build process with references to your app’s resources. Every resource you create (or which is provided by Android) is referenced by an integer in R , called a resource id.

R.layout.* references any layout resource you have created, usually in /res/layout . So if you created an activity layout called activity_main.xml , you can then use the reference in R.layout.activity_main to access it. Many built-in functionality readily accepts such a resource id, for example setContentView(int layoutResid) which you use during the creation of your activity and where you probably encountered this particular example.

If you create a string resource (in strings.xml) like this:

it will get a new reference in R.string.app_name . You can then use this everywhere where a string resource is accepted, for example the android:label for your application in AndroidManifest.xml , or on a TextView; either in the xml:

 android:layout_width="wrap_content" 
android:layout_height="wrap_content" 
android:text="@string/app_name" 
/>

or in code: textview.setText(R.string.app_name) .

You can access resources programmatically using the Resources class, to which you can get a reference by calling getResources on any context (like your activity). So for example you can get your app name described above in your activity by calling this.getResources().getString(R.string.app_name) .

You can also supply different resources for different device properties/settings (like screen size or language), which you can access using the same references in R . The easiest example here, imho, is strings: if you add a new values folder in /res with a language specifier (so /res/values-nl for Dutch) and you add strings with the same identifier but a different translation and the resource management system cleverly figures out which one to provide for you based on your user’s device.

I hope this helps a bit. For more information on resources see the documentation.

the R.java file in android studio 3.4

\app\build\generated\not_namespaced_r_class_sources\debug\processDebugResources\r\\R.java

package_name_tree means : If package is a.b.c
the goto: /a/b/c/R.java

Why I do not need to import the android R class?

It is because your MainActivity.java are inside the package name which is the same as package name declared in AndroidManifest.xml :

package=»tld.mydomain.buttonclickcounter»>

The R.java will be generated based on the package name in AndroidManifest.xml . So, if you’re using other package name like tld.mydomain :

you then need to import the R.java with tld.mydomain.R .

Источник