问DateTimeFormatter不适用于低于8的Android版本。

EN

android {

    defaultConfig {
        // Required when setting minSdkVersion to 20 or lower
        multiDexEnabled true
    }

    compileOptions {
        // Flag to enable support for the new language APIs
        coreLibraryDesugaringEnabled true
        // Sets Java compatibility to Java 8
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {

    coreLibraryDesugaring 'com.android.tools:desugar_jdk_libs:1.1.5'
}