Animation qui ne se lance pas.

Salut, quelqu'un saurait pourquoi cette anim ne se lance pas ?:

res/anim/ma_premiere_anim.xml:

Code:

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<?xml version="1.0" encoding="utf-8"?>
<set xmlns:android="http://schemas.android.com/apk/res/android">
    <scale
        android:fromXScale="1.0"
        android:fromYScale="1.0"
        android:toXScale="2.0"
        android:toYScale="0.5"
        android:pivotX="50%"
        android:pivotY="50%"
        android:duration="300"/>
    <alpha
        android:fromAlpha="1.0"
        android:toAlpha="0.0"
        android:startOffset="300"
        android:duration="2000"/>
</set>

MainActivity:

Code:

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import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.TextView;
 
public class MainActivity extends AppCompatActivity {
 
    TextView hello;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        hello = (TextView) findViewById(R.id.hello);
 
        Animation animation = AnimationUtils.loadAnimation(this, R.anim.ma_premiere_anim);
        hello.startAnimation(animation);
    }
}

layout activity_main:

Code:

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<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context=".MainActivity">
 
    <TextView
        android:id="@+id/hello"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />
 
</android.support.constraint.ConstraintLayout>

J'ai beau comprendre chaque ligne de ce que j'ai codé je ne comprends pas pourquoi l'anim ne se lance pas.. Merci d'avance :)