无法在活动中显示背景颜色

Question

这是我的XML文件。我在运行我的应用程序时遇到了麻烦。我已经为注册活动创建了相同的GUI，但在设计登录活动时遇到问题。我已经宣布tools:background = "@color/colorPrimary"但无法获得colorPrimary。我该怎么做才能解决这个错误。为什么我收到这个错误。帮我。

<android.support.constraint.ConstraintLayout 
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"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:background="@color/colorPrimary"
tools:context="com.example.pratikrathi.registerapp.RegisterActivity">
<EditText
    android:id="@+id/reg_email_text"
    android:layout_width="0dp"
    android:layout_height="54dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="200dp"
    android:backgroundTint="@android:color/white"
    android:ems="10"
    android:hint="@string/email_hint"
    android:inputType="textEmailAddress"
    android:paddingVertical="16dp"
    android:textColor="@android:color/white"
    android:textColorHint="@color/whiteTransparentHalf"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/login_progress" />
<EditText
    android:id="@+id/reg_password_text"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:backgroundTint="@android:color/white"
    android:ems="10"
    android:hint="@string/password_hint"
    android:inputType="textPassword"
    android:paddingVertical="16dp"
    android:textColor="@android:color/white"
    android:textColorHint="@color/whiteTransparentHalf"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/reg_email_text" />
<Button
    android:id="@+id/login_btn"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:backgroundTint="@color/colorAccent"
    android:paddingBottom="20dp"
    android:paddingTop="20dp"
    android:text="@string/login_btn_text"
    android:textAllCaps="false"
    android:textColor="@android:color/white"
    android:textSize="14sp"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/reg_password_text" />
<Button
    android:id="@+id/login_reg_btn"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginBottom="4dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:backgroundTint="@android:color/white"
    android:paddingBottom="20dp"
    android:paddingTop="20dp"
    android:text="@string/login_reg_btn_text"
    android:textAllCaps="false"
    android:textColor="@color/colorAccent"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintStart_toStartOf="parent" />
<ProgressBar
    android:id="@+id/login_progress"
    style="?android:attr/progressBarStyleHorizontal"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:indeterminate="true"
    android:visibility="invisible"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />
 </android.support.constraint.ConstraintLayout>

Answer 1

只需将tools:background="@color/colorPrimary"更改为android:background="@color/colorPrimary"，

因为工具在预览中用于android studio中的可见性

Answer 2

添加以下代码，您要在其中应用背景：

style="@style/style1"

值/ style.xml

<style name="style1">
    <item name="android:background">@drawable/custom_color</item>
</style>

绘制\ custom_color.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item>
    <shape>
        <solid android:color="@color/custom_color" />
    </shape>
</item>

值\ colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
<color name="custom_color">#123456</color>
</resources>