ZXingLite/app/src/main/res/layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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:context=".MainActivity">
    <androidx.appcompat.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:background="@color/colorPrimary"
        android:layout_height="wrap_content"
        app:contentInsetLeft="0dp"
        app:contentInsetStart="0dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintTop_toTopOf="parent">
        <TextView
            android:id="@+id/tvTitle"
            android:layout_width="match_parent"
            android:layout_height="@dimen/title_height"
            android:gravity="center"
            android:singleLine="true"
            android:textSize="@dimen/size_18sp"
            android:textColor="@color/white"
            android:layout_gravity="center_horizontal"
            android:text="@string/app_name"/>
    </androidx.appcompat.widget.Toolbar>
    <Button
        android:id="@+id/btn0"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="16dp"
        android:layout_marginBottom="6dp"
        android:text="默认扫码"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/toolbar"
        style="@style/OnClick"/>
    <Button
        android:id="@+id/btn1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="6dp"
        android:layout_marginBottom="6dp"
        android:text="连续扫码"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn0"
        style="@style/OnClick"/>
    <Button
        android:id="@+id/btn2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="6dp"
        android:layout_marginBottom="6dp"
        android:text="Fragment扫码"
        android:textAllCaps="false"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn1"
        style="@style/OnClick"/>
    <Button
        android:id="@+id/btn3"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="6dp"
        android:layout_marginBottom="6dp"
        android:text="自定义布局扫码"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn2"
        style="@style/OnClick"/>
    <Button
        android:id="@+id/btn4"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="6dp"
        android:layout_marginBottom="6dp"
        android:text="自定义全屏扫二维码"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn3"
        style="@style/OnClick"/>
    <Button
        android:id="@+id/btn5"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="6dp"
        android:layout_marginBottom="6dp"
        android:text="生成条形码"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn4"
        style="@style/OnClick"/>
    <Button
        android:id="@+id/btn6"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="6dp"
        android:layout_marginBottom="6dp"
        android:text="生成二维码"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn5"
        style="@style/OnClick"/>
    <Button
        android:id="@+id/btn7"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="6dp"
        android:layout_marginBottom="6dp"
        android:text="识别一维码/二维码图片"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn6"
        style="@style/OnClick"/>
    <Button
        android:id="@+id/btn8"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="6dp"
        android:layout_marginBottom="6dp"
        android:text="只识别二维码"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/btn7"
        style="@style/OnClick"/>
</androidx.constraintlayout.widget.ConstraintLayout>