来源在这里(https://github.com/googlecodelabs/constraint-layout).

根据下面的说明,它表示添加垂直屏障,但我没有在菜单中看到添加选项.实际上整个菜单选项看起来不同. “添加垂直屏障”菜单在哪里？

Right click on ConstraintLayout in the blueprint or the Component
Tree. You will see the Add Vertical barrier and Add Horizontal barrier
options.

我正在运行Android 2.3.3.

build.gradle(模块：app)

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.3"
    defaultConfig {
        applicationId "com.google.googleio"
        minSdkVersion 22
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'),'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs',include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support.constraint:constraint-layout:1.1.0-beta1'
}