I'm trying to have a TextView generate a random number every 472 ms, five times. How would I use a loop to do this?

user10408802

So, I have a TextView that generates a random number. I need that TextView to generate a random number every 472 ms, five times. So I tap the screen and a random number appears then 472 ms later another number appears, and this repeats until five random numbers have been displayed. I know I need to use a loop but what condition would I use to make sure that only five random numbers are generated?

Here's my XML:

<LinearLayout
    android:id="@+id/linearLayout"
    android:layout_width="0dp"
    android:layout_height="0dp"
    android:clickable="true"
    android:onClick="perform_action"
    android:orientation="vertical"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/textView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:layout_gravity="center_horizontal|center_vertical"
            android:layout_marginBottom="75dp"
            android:gravity="center"
            android:textSize="400sp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintStart_toStartOf="parent" />

    </RelativeLayout>

</LinearLayout>
</android.support.constraint.ConstraintLayout>

And my Java:

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

public void perform_action(View view) {
    Random r = new Random();
    int minNumber = 1;
    int maxNumber = 9;
    int randomNumber = r.nextInt((maxNumber-minNumber)+1)+minNumber;
    TextView tv = (TextView) findViewById(R.id.textView1);
    tv.setText(String.valueOf(randomNumber));
}
}

Samuel Eminet

You should use rxjava

add these dependencies :

implementation 'io.reactivex.rxjava2:rxjava:2.2.2'
implementation 'io.reactivex.rxjava2:rxandroid:2.1.0'

and then when you click your button :

final List< Integer > randomNumbers = new ArrayList<>( );
Observable.intervalRange( 0, 5, 0, 472, TimeUnit.MILLISECONDS )
        .map( aLong -> {
            int previous = randomNumbers.size( ) > 0 ? randomNumbers.get(
                    randomNumbers.size( ) - 1 ) : -1;
            int randomNumber = generateRandomNumber();
            while( randomNumber == previous ) generateRandomNumber();
            randomNumbers.add( randomNumber );
            return randomNumber;
        } )
        .observeOn( AndroidSchedulers.mainThread( ) )
        .subscribe(integer -> {
            TextView tv = (TextView) findViewById(R.id.textView1);
            tv.setText(String.valueOf(integer));
        } );

private int generateRandomNumber( )
{
    Random r = new Random( );
    int minNumber = 1;
    int maxNumber = 9;
    return r.nextInt( ( maxNumber - minNumber ) + 1 ) + minNumber;
}

That's it!

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