出现五个随机数后如何让我的屏幕变黑？

Question

I'm new to coding and need all the help I can get. I'm creating an app that displays a random number every 472ms, five times and then will clear the screen after all five numbers have appeared. When you press the screen, it'll repeat that action. I've got the numbers to appear randomly and on time but I don't know how to clear the screen after the numbers have displayed each time.

This is what I mean:

Press screen -> a random appears every 472ms until five numbers have been displayed -> screen goes blank -> press screen -> order repeats

How would I make the screen go blank after those five numbers appear?

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:

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.TimeUnit;
import io.reactivex.Observable;
import io.reactivex.android.schedulers.AndroidSchedulers;


public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}

public void perform_action(View view) {
    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) randomNumber = 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;
}
    }

Answer 1

You pass a Consumer to onNext in .subscribe, also add one to onComplete:

.subscribe(integer -> {
    TextView tv = (TextView) findViewById(R.id.textView1);
    tv.setText(String.valueOf(integer));
}, error -> {}, () -> {
    TextView tv = (TextView) findViewById(R.id.textView1);
    tv.setText("");

}

This would happen directly after the fifth one appeared. As a workaround you can change the intervalRange to 6 times.