package com.example.partition;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

public class QuadratureView extends View {
    private Paint paint;
    private int color;

    public QuadratureView(Context context, AttributeSet attrs) {
        super(context, attrs);
        paint = new Paint();
    }

    public void setColor(int color) {
        this.color = color;
        invalidate();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        paint.setColor(color);
        canvas.drawRect(0, 0, getWidth(), getHeight(), paint);
    }
}

Modifications dans activity_main.xml (remplacement des <View> par <com.example.partition.QuadratureView>)

<com.example.partition.QuadratureView
    android:layout_width="100dp"
    android:layout_height="100dp"
    android:layout_alignParentTop="true"
    android:layout_alignParentStart="true"
    android:background="#AACCEE"/>

(Faire de même pour les autres View)