Android Studio can't find activity

Question

I am working with Android Studio 1.0 when suddenly, out of the blue I can not run my app on my phone because it is telling me that it can not find the default activity.

Changing the "default activity" to the specific activity I want to launch, ends in the error that apparently the activity I selected is not declared in AndroidManifest.xml. Which also isn't true, because I did declare it in the .xml, I didn't remove it or add something new, it always has been there and now it doesn't want to work.

Thank you for reading and maybe answering / commenting. :D

Edit: This is my AndroidManifest.xml:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="pack.aproject" >

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".SecondPageActivity">

        </activity>
    </application>

</manifest>

Answer 1

you may need to refresh the IDE's cache.

File -> Invalidate Caches / Restart...