package android.support.v4.app does not exist ; in Android studio 0.8

@boernard 's answer solves this from the Android Studio IDE, but if you want to understand what's happening under the covers, it's a simple gradle build file update:

You can edit the build.gradle file from within the IDE (left pane: Gradle Scripts -> build.gradle (Module: app)) or use the raw path (<proj_dir>/app/build.gradle) and add/update the following dependency section:

dependencies {
    //
    // IDE setting pulls in the specific version of v4 support you have installed:
    //
    //compile 'com.android.support:support-v4:21.0.3'

    //
    // generic directive pulls in any available version of v4 support:
    //
    compile 'com.android.support:support-v4:+'
}

Using the above generic compile directive, allows you to ship your code to anyone, provided they have some level of the Android Support Libraries v4 installed.

Ok, so I had the same problem and found a solution in a udacity forum:

In Android Studio:

1. Right click on your projects "app" folder and click on -> module settings
2. Click on the "dependencies" tab
3. Click on the + sign to add a new dependency and select "Library Dependency"
4. Look for the library you need and add it

None of the above solutions worked for me. What finally worked was:

Instead of

import android.support.v4.content.FileProvider;

Use this

import androidx.core.content.FileProvider;

This path is updated as of AndroidX (the repackaged Android Support Library).