Components are not in class R

Question

I’m building an agenda, and for that I’ve created a Activity where would be a list of all contacts:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".actContato">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">

        <EditText
            android:id="@+id/edtPesquisa"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:ems="10"
            android:hint="@string/lbl_hint_nome_pesquisa"
            android:inputType="textPersonName" />

        <ImageButton
            android:id="@+id/imb_ADD"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@android:drawable/ic_menu_add" />

    </LinearLayout>

    <ListView
        android:id="@+id/lstContatos"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="1" />

</LinearLayout>

And another Activity where all contacts would be registered:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="aula4.com.example.raru.agenda.ActContatos">

    <LinearLayout
        android:id="@+id/lnlNome"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <TextView
            android:id="@+id/txtNomeContato"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/lblNomeContato"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <EditText
            android:id="@+id/edtNome"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:ems="10"
            android:hint="@string/lbl_hint_nome"
            android:inputType="textPersonName" />

        <EditText
            android:id="@+id/edtSobreNome"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:hint="@string/lbl_hint_sobrenome"
            android:inputType="textPersonName" />
    </LinearLayout>

    <LinearLayout
        android:id="@+id/lnlTelefone"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:orientation="vertical">

        <TextView
            android:id="@+id/txtTelefone"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/lblTelefone"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:orientation="horizontal">

            <EditText
                android:id="@+id/edtTelefone"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:ems="10"
                android:inputType="phone" />

            <Spinner
                android:id="@+id/spnTelefone"
                android:layout_width="150dp"
                android:layout_height="wrap_content"
                android:layout_weight="1" />
        </LinearLayout>

    </LinearLayout>

    <LinearLayout
        android:id="@+id/lnlEmail"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:orientation="vertical">

        <TextView
            android:id="@+id/txtEmail"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/lblEmail"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:orientation="horizontal">

            <EditText
                android:id="@+id/edtEmail"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:ems="10"
                android:inputType="textEmailAddress" />

            <Spinner
                android:id="@+id/spnEmail"
                android:layout_width="150dp"
                android:layout_height="wrap_content"
                android:layout_weight="1" />
        </LinearLayout>
    </LinearLayout>

    <LinearLayout
        android:id="@+id/lnlEndereco"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:orientation="vertical">

        <TextView
            android:id="@+id/txtEndereco"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/lblEndereco"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:orientation="horizontal">

            <EditText
                android:id="@+id/edtEndereco"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:ems="10"
                android:inputType="textPostalAddress" />

            <Spinner
                android:id="@+id/spnEndereco"
                android:layout_width="150dp"
                android:layout_height="wrap_content"
                android:layout_weight="1" />
        </LinearLayout>
    </LinearLayout>

    <LinearLayout
        android:id="@+id/lnlDatasEspeciais"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:orientation="vertical">

        <TextView
            android:id="@+id/txtDatas"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/lblDatas"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:orientation="horizontal">

            <EditText
                android:id="@+id/edtDatas"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:ems="10"
                android:inputType="date" />

            <Spinner
                android:id="@+id/spnDatas"
                android:layout_width="150dp"
                android:layout_height="wrap_content"
                android:layout_weight="1" />
        </LinearLayout>
    </LinearLayout>

    <LinearLayout
        android:id="@+id/lnlGrupo"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:orientation="vertical">

        <TextView
            android:id="@+id/txtGrupos"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/lblGrupos"
            android:textAppearance="?android:attr/textAppearanceMedium" />

        <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:orientation="horizontal">

            <EditText
                android:id="@+id/edtGrupos"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:ems="10"
                android:inputType="text" />

        </LinearLayout>

    </LinearLayout>

</LinearLayout>

But when it comes to getting the reference in the java classes of both Activity (findViewById()), is pointed out that there is no reference to the xml components.

I took a look at the R class and there’s really no reference to them.

OBS: I remembered that this error only happened after editing the xml menu, before I could even perform tests by the virtual machine, I already removed all the modifications and left the xml as before:

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context="aula4.com.example.raru.agenda2.ActContatos">

    <item
        android:id="@+id/action_settings"
        android:orderInCategory="100"
        android:title="@string/action_settings"
        app:showAsAction="never" />
</menu>

and:

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context=".actContato">

    <item
        android:id="@+id/action_settings"
        android:orderInCategory="100"
        android:title="@string/action_settings"
        app:showAsAction="never" />
</menu>

Mistakes:

Answer 1

The error is not in the generation of the R class or in the layout, but in the build.Gradle file, that is, your project build configuration file. The two images you posted clearly show that the error has nothing to do with the layout. Be sure to fix the errors indicated in the lower left panel of the second image and correctly write your build file. After everything is fixed, give a clean + rebuild on the project.

Answer 2

Try the following, comment or remove all lines with errors, give a clean on your project and then build. The elements will likely reappear in the R class.

The R class is automatically generated having all the elements of its layouts in it, but in some types of errors in your code it may not be generated or not fully generated.

Answer 3

Try two things:

1º In Android Studio click on "Build" and then on "Clean Project" 2nd Click again on "Build" click on "Rebuild Project"

See if it solves