Error: package android.support.v7.app does not exist [ANDROID STUDIO]

Question

I'm trying to compile a project using Android Studio and this error show up. I've already imported the appcompat in the build.gradle file:

dependencies {
    compile 'com.android.support:support-v4:21.0.+'
    compile 'com.android.support:appcompat-v7:21.0.+'
    compile 'com.melnykov:floatingactionbutton:1.1.0'
}

and in several files I've imported this:

import android.support.v7.app.ActionBarActivity;

Answer 1

Remove this dependency from Gradle file and add from

Project(right click) -> Project Structure ->click on your application-> Dependencies -> Add button(right side) ->library dependency -> Choose V7 libary.

Similarly add the module dependency using this way. Also before building the project make sure you do the same to the module project

Answer 2

运行gradle clean build命令