Q:

Animation splash screen of toolbar resizing

EDIT2
Everything works now, except for floating action button's onclick listener doesn't work. 

EDIT
Ok so i've come with a semi-solution
I've removed AppBarLayout from activity_main.xml, and now it does not flicker anymore.  The only thing is that the action bar is completely white, and does not merge with the toolbar color.  How could i fix this? 

I've followed this site in order to achieve this animation(without recycler view though):

The only thing is that mine is flickering a lot and I don't know where could be the issue.  Also the toolbar gets to small than the default size.  Thank you
MainActivity.java
public class MainActivity extends AppCompatActivity {
private final String PREFS_NAME = "MyPrefsFile";
private boolean doubleBackToExitPressedOnce = false;
private CoordinatorLayout main_content;
private FloatingActionButton fab;
private int mContentViewHeight;
private Toolbar mToolbar;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    this.setTitle(getString(R.string.title_main_activity));
    main_content = (CoordinatorLayout) findViewById(R.id.main_content);

    fab = (FloatingActionButton) findViewById(R.id.fab);/*
    fab.setOnClickListener(new View. OnClickListener() {
        @Override
        public void onClick(View view) {
            startActivity(new Intent(MainActivity.this, BasicActivity.class));
        }
    });*/
    // Fake a long startup time
    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            onFakeCreate();
        }

    }, 100);
}

    private void onFakeCreate() {
        setContentView(R.layout.activity_onboarding_placeholder);

        TextView titleTextView = (TextView) findViewById(R.id.text_title);
        ViewCompat.animate(titleTextView).alpha(1).start();

        mToolbar = (Toolbar) findViewById(R.id.toolbar);
        mToolbar.getViewTreeObserver().addOnPreDrawListener(
                new ViewTreeObserver. OnPreDrawListener() {
                    @Override
                    public boolean onPreDraw() {
                        mToolbar.getViewTreeObserver().removeOnPreDrawListener(this);
                        final int widthSpec = View. MeasureSpec.makeMeasureSpec(0, View. MeasureSpec. UNSPECIFIED);
                        final int heightSpec = View. MeasureSpec.makeMeasureSpec(0, View. MeasureSpec. UNSPECIFIED);

                        mToolbar.measure(widthSpec, heightSpec);
                        mContentViewHeight = mToolbar.getHeight();
                        collapseToolbar();
                        return true;
                    }
                });
    }

    private void collapseToolbar() {
        int toolBarHeight;
        TypedValue tv = new TypedValue();
        getTheme().resolveAttribute(android. R.attr.actionBarSize, tv, true);
        toolBarHeight = TypedValue.complexToDimensionPixelSize(
                tv.data, getResources().getDisplayMetrics());

        ValueAnimator valueHeightAnimator = ValueAnimator
                .ofInt(mContentViewHeight, toolBarHeight);

        valueHeightAnimator.addUpdateListener(
                new ValueAnimator. AnimatorUpdateListener() {

                    @Override
                    public void onAnimationUpdate(ValueAnimator animation) {
                        ViewGroup. LayoutParams lp = mToolbar.getLayoutParams();
                        lp.height = (Integer) animation.getAnimatedValue();
                        mToolbar.setLayoutParams(lp);
                    }
                });

        valueHeightAnimator.start();
        valueHeightAnimator.addListener(
                new AnimatorListenerAdapter() {

                    @Override
                    public void onAnimationEnd(Animator animation) {
                        super.onAnimationEnd(animation);

                        // Animate fab
                        ViewCompat.animate(fab).setStartDelay(600)
                                .setDuration(400).scaleY(1).scaleX(1).start();

                    }
                });
    }
[...]

Splash_background.xml
<? xml version="1.0" encoding="utf-8"? >
<layer-list
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:opacity="opaque"
    >
    <item>
        <shape>
            <solid android:color="@color/background"/>
        </shape>
    </item>

    <item
        android:height="180dp"
        android:gravity="top">
        <shape android:shape="rectangle">
            <solid android:color="?colorPrimary"/>
        </shape>
    </item>
</layer-list>

activity_main.xml(updated)
<? xml version="1.0" encoding="utf-8"? >
<android.support.design.widget. CoordinatorLayout
    android:id="@+id/main_content"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="">

        <android.support.v7.widget. Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="156dp"
    android:background="?colorPrimary"
    android:elevation="4dp"
    app:theme="@style/ThemeOverlay. AppCompat. Light"/>

    <android.support.design.widget. FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        android:src="@drawable/ic_add_white_24dp"
        app:fabSize="normal"/>

</android.support.design.widget. CoordinatorLayout>

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

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

                <category android:name="android.intent.category. LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=". BasicActivity"
            android:label="@string/title_activity_basic"
            android:parentActivityName=". MainActivity">
            <meta-data
                android:name="android.support. PARENT_ACTIVITY"
                android:value="" />
        </activity>
        <activity
            android:name=". ExtraActivity"
            android:label="@string/title_activity_extra"
            android:parentActivityName=". BasicActivity">
            <meta-data
                android:name="android.support. PARENT_ACTIVITY"
                android:value="" />
        </activity>
    </application>

</manifest>

A:

Please check the style in your project.toolbar animation working fine at my side. 
    <resources>
    <style name="Button" parent="Theme. AppCompat">
        <item name="colorControlHighlight">@color/indigo_500</item>
        <item name="colorButtonNormal">@color/pink_200</item>
    </style>
</resources>

also check the build gradle
    apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.2"

    defaultConfig {
        applicationId ""
        minSdkVersion 21
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.1.1'
    compile 'com.android.support:cardview-v7:23.1.1'
    compile 'com.android.support:recyclerview-v7:23.1.1'
    compile 'com.android.support:design:23.1.1'
}

Hope this helps.:)