Error: cannot find symbol class Compilation
<p>I made my app successfully. Now, after following this tutorial(<a href="http://androidmkab.com/2016/02/23/android-implementing-admob-interstitial-ad-and-banner-ad-in-android-app/" rel="nofollow noreferrer">Implementing AdMob into your app</a>), I started to receive errors. After researching for over 4 days, I've found no solution so far. I've tried renaming the classes, but that did not do any good. I did clean my project, which was successful, but when I rebuilt it, I received the following errors:</p>
<blockquote>
<p>Error:(59, 13) error: cannot find symbol class InterstitialAd</p>
<p>Error:(60, 5) error: cannot find symbol class InterstitialAd</p>
<p>Error:(70, 9) error: cannot find symbol class AdView</p>
<p>Error:(70, 27) error: cannot find symbol class AdView</p>
<p>Error:(71, 9) error: cannot find symbol class AdRequest</p>
<p>Error:(71, 44) error: package AdRequest does not exist</p>
<p>Error:(75, 28) error: cannot find symbol class InterstitialAd</p>
<p>Error:(81, 40) error: cannot find symbol class AdListener</p>
</blockquote>
<p>Here's the Script for MainActivity.java:</p>
<pre><code>package com.mycompany.testimage;

import com.mycompany.testimage.R;
import android.annotation.TargetApi;
import android.graphics.RectF;
import android.os.Build;
import android.os.Bundle;
import android.os.Handler;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.util.SparseArrayCompat;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.Toolbar;
import android.text.Spannable;
import android.text.SpannableString;
import android.util.TypedValue;
import android.view.View;
import android.view.animation.AccelerateDecelerateInterpolator;
import android.widget.ImageView;
import android.widget.ScrollView;
import android.widget.TextView;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.content.Intent;

import com.astuetz.PagerSlidingTabStrip;
import com.flaviofaria.kenburnsview.KenBurnsView;
import com.nineoldandroids.view.ViewHelper;

import java.util.Random;

public class MainActivity extends ActionBarActivity implements ScrollTabHolder, ViewPager.OnPageChangeListener {

private static AccelerateDecelerateInterpolator sSmoothInterpolator = new AccelerateDecelerateInterpolator();

private KenBurnsView mHeaderPicture;
private View mHeader;
private PagerSlidingTabStrip mPagerSlidingTabStrip;
private ViewPager mViewPager;
private PagerAdapter mPagerAdapter;
private Toolbar toolbar;
private TextView title;
private ImageView icon;
private int mActionBarHeight;
private int mMinHeaderHeight;
private int mHeaderHeight;
private int mMinHeaderTranslation;
private ImageView mHeaderLogo;
private RectF mRect1 = new RectF();
private RectF mRect2 = new RectF();
private TypedValue mTypedValue = new TypedValue();
private SpannableString mSpannableString;
private AlphaForegroundColorSpan mAlphaForegroundColorSpan;
private InterstitialAd interstitial;
InterstitialAd mInterstitialAd;

int[] photos={R.drawable.photo1, R.drawable.phpto2, R.drawable.photo3, R.drawable.photo4, R.drawable.photo5, R.drawable.photo6, R.drawable.photo7, R.drawable.photo8, R.drawable.photo9};
KenBurnsView imageView;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    AdView mAdView = (AdView) findViewById(R.id.adView);
    AdRequest adRequest = new AdRequest.Builder().build();
    mAdView.loadAd(adRequest);

// Prepare the Interstitial Ad
    interstitial = new InterstitialAd(MainActivity.this);
// Insert the Ad Unit ID
    interstitial.setAdUnitId(getString(R.string.admob_interstitial_id));

    interstitial.loadAd(adRequest);
// Prepare an Interstitial Ad Listener
    interstitial.setAdListener(new AdListener() {
        public void onAdLoaded() {
            // Call displayInterstitial() function
            displayInterstitial();
        }
    });

    mMinHeaderHeight = getResources().getDimensionPixelSize(R.dimen.min_header_height);
    mHeaderHeight = getResources().getDimensionPixelSize(R.dimen.header_height);
    mMinHeaderTranslation = -mMinHeaderHeight + getActionBarHeight();

    setContentView(R.layout.activity_main);
    imageView =(KenBurnsView) findViewById(R.id.header_picture);
    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    icon = (ImageView) findViewById(R.id.icon);
    title = (TextView) findViewById(R.id.title);
    mSpannableString = new SpannableString(getString(R.string.actionbar_title));

    mHeaderLogo = (ImageView) findViewById(R.id.header_thumbnail);
    mHeader = findViewById(R.id.header);
    mPagerSlidingTabStrip = (PagerSlidingTabStrip) findViewById(R.id.tabs);
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setOffscreenPageLimit(4);
    mPagerAdapter = new PagerAdapter(getSupportFragmentManager());
    mPagerAdapter.setTabHolderScrollingContent(this);
    mViewPager.setAdapter(mPagerAdapter);
    mPagerSlidingTabStrip.setViewPager(mViewPager);
    mPagerSlidingTabStrip.setOnPageChangeListener(this);
    mAlphaForegroundColorSpan = new AlphaForegroundColorSpan(0xffffffff);
    ViewHelper.setAlpha(getActionBarIconView(), 0f);

    getSupportActionBar().setBackgroundDrawable(null);

    final Handler handler = new Handler();
    Runnable runnable = new Runnable() {
        int i=0;
        public void run() {
            // change images randomly
            Random ran=new Random();
            int i=ran.nextInt(photos.length);
            //set image resources
            imageView.setImageResource(photos[i]);
            i++;
            if(i&gt;photos.length-1)
            {
                i=0;
            }
            handler.postDelayed(this, 7000);  //for interval...
        }
    };
    handler.postDelayed(runnable, 7000); //for initial delay..
}

public void displayInterstitial() {
// If Ads are loaded, show Interstitial else show nothing.
    if (interstitial.isLoaded()) {
        interstitial.show();
    }
}

@Override
public void onPageScrollStateChanged(int arg0) {
    // nothing
}

@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
    // nothing
}

@Override
public void onPageSelected(int position) {
    SparseArrayCompat&lt;ScrollTabHolder&gt; scrollTabHolders = mPagerAdapter.getScrollTabHolders();
    ScrollTabHolder currentHolder = scrollTabHolders.valueAt(position);
    currentHolder.adjustScroll((int) (mHeader.getHeight() + ViewHelper.getTranslationY(mHeader)), mHeaderHeight);

}

@Override
public void onScroll(ScrollView view, int x, int y, int oldX, int oldY, int pagePosition)
{
    if (mViewPager.getCurrentItem() == pagePosition)
    {
        mHeader.setTranslationY(Math.max(-view.getScrollY(), mMinHeaderTranslation));
        float ratio = clamp(mHeader.getTranslationY() / mMinHeaderTranslation, 0.0f, 1.0f);
        interpolate(mHeaderLogo, getActionBarIconView(), sSmoothInterpolator.getInterpolation(ratio));
        setTitleAlpha(clamp(5.0F * ratio - 4.0F, 0.0F, 1.0F));
    }
}

@Override
public void adjustScroll(int scrollHeight,int headerTranslationY) {
    // nothing
}



public static float clamp(float value, float max, float min) {
    return Math.max(Math.min(value, min), max);
}

private void interpolate(View view1, View view2, float interpolation) {
    getOnScreenRect(mRect1, view1);
    getOnScreenRect(mRect2, view2);

    float scaleX = 1.0F + interpolation * (mRect2.width() / mRect1.width() - 1.0F);
    float scaleY = 1.0F + interpolation * (mRect2.height() / mRect1.height() - 1.0F);
    float translationX = 0.5F * (interpolation * (mRect2.left + mRect2.right - mRect1.left - mRect1.right));
    float translationY = 0.5F * (interpolation * (mRect2.top + mRect2.bottom - mRect1.top - mRect1.bottom));

    ViewHelper.setTranslationX(view1, translationX);
    ViewHelper.setTranslationY(view1, translationY - ViewHelper.getTranslationY(mHeader));
    ViewHelper.setScaleX(view1, scaleX);
    ViewHelper.setScaleY(view1, scaleY);
}

private RectF getOnScreenRect(RectF rect, View view) {
    rect.set(view.getLeft(), view.getTop(), view.getRight(), view.getBottom());
    return rect;
}

@TargetApi(Build.VERSION_CODES.HONEYCOMB)
public int getActionBarHeight() {
    if (mActionBarHeight != 0) {
        return mActionBarHeight;
    }

    if(Build.VERSION.SDK_INT &gt; Build.VERSION_CODES.HONEYCOMB){
        getTheme().resolveAttribute(android.R.attr.actionBarSize, mTypedValue, true);
    }else{
        getTheme().resolveAttribute(R.attr.actionBarSize, mTypedValue, true);
    }

    mActionBarHeight = TypedValue.complexToDimensionPixelSize(mTypedValue.data, getResources().getDisplayMetrics());

    return mActionBarHeight;
}

private void setTitleAlpha(float alpha) {
    mAlphaForegroundColorSpan.setAlpha(alpha);
    mSpannableString.setSpan(mAlphaForegroundColorSpan, 0, mSpannableString.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
    title.setText(mSpannableString);
}

private ImageView getActionBarIconView() {
    return icon;
}

public class PagerAdapter extends FragmentPagerAdapter {

    private SparseArrayCompat&lt;ScrollTabHolder&gt; mScrollTabHolders;
    private final String[] TITLES = { &quot;Home&quot;, &quot;Install&quot;, &quot;About&quot;, &quot;Media&quot;, &quot;Survey&quot;, &quot;Upcoming&quot;, &quot;News&quot;, &quot;Help&quot;, &quot;Credits&quot;, &quot;Share&quot;, &quot;More&quot;};
    private ScrollTabHolder mListener;

    public PagerAdapter(FragmentManager fm) {
        super(fm);
        mScrollTabHolders = new SparseArrayCompat&lt;ScrollTabHolder&gt;();
    }

    public void setTabHolderScrollingContent(ScrollTabHolder listener) {
        mListener = listener;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return TITLES[position];
    }

    @Override
    public int getCount() {
        return TITLES.length;
    }

    @Override
    public Fragment getItem(int position) {
        ScrollTabHolderFragment fragment = (ScrollTabHolderFragment) ScrollViewFragment.newInstance(position);
        mScrollTabHolders.put(position, fragment);
        if (mListener != null) {
            fragment.setScrollTabHolder(mListener);
        }
        return fragment;
    }

    public SparseArrayCompat&lt;ScrollTabHolder&gt; getScrollTabHolders() {
        return mScrollTabHolders;
    }

    }

    public class LinkButtons extends Activity {

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.main);
        }

        public void goToSo (View view) {
            goToUrl ( &quot;http://stackoverflow.com/&quot;);
        }

        public void goToSu (View view) {
            goToUrl ( &quot;http://superuser.com/&quot;);
        }

        private void goToUrl (String url) {
            Uri uriUrl = Uri.parse(url);
            Intent launchBrowser = new Intent(Intent.ACTION_VIEW, uriUrl);
            startActivity(launchBrowser);
        }

    }

}
</code></pre>
<p>Android build.gradle</p>
<pre><code>apply plugin: 'com.android.application'

android {
compileSdkVersion 21
buildToolsVersion &quot;21.0.1&quot;

defaultConfig {
    applicationId &quot;com.xrevolt.mmxstructures&quot;
    minSdkVersion 14
    targetSdkVersion 21
    versionCode 2
    versionName &quot;1.2.0&quot;
}

buildTypes {
    release {
        apply plugin: 'announce'
        /*
        runProguard false
        */
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
}

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:21.0.+'
compile 'com.android.support:cardview-v7:21+'
compile 'com.flaviofaria:kenburnsview:1.0.5'
compile 'com.jpardogo.materialtabstrip:library:1.0.6'
compile 'com.nineoldandroids:library:2.4.0'
compile 'com.google.android.gms:play-services-ads:8.4.0'
}
</code></pre>