activity_main.xml

<com.test.graphvisualizer.Graph
    android:id="@+id/graph"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	app:layout_constraintBottom_toTopOf="parent"
	app:layout_constraintBottom_toBottomOf="parent"
	app:layout_constraintLeft_toLeftOf="parent"
	app:layout_constraintRight_toRightOf="parent"
	app:layout_constraintTop_toTopOf="parent"
	android:paddingLeft="35dp"
	android:paddingStart="35dp"
	android:paddingRight="35dp"
	android:paddingEnd="35dp"
	android:paddingTop="100dp"
	android:paddingBottom="100dp"
	app:gradColorStart="@color/greenDark"
	app:gradColorEnd="@color/greenLight"
	app:markerColor="@color/greenDark"
	app:connectedLinesColor="@color/greenDark"
	app:guidelinesColor="@color/gray"
	app:graduationColor="@color/gray" />

attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
	<declare-styleable name="Graph">
		<attr name="gradColorStart" format="color"/>
		<attr name="gradColorEnd" format="color"/>
		<attr name="markerColor" format="color"/>
		<attr name="connectedLinesColor" format="color"/>
		<attr name="guidelinesColor" format="color"/>
		<attr name="graduationColor" format="color"/>
	</declare-styleable>
</resources>

Graph.java

public class Graph extends View {
    
    private Paint paint;
    private Paint gradientPaint;
    private Paint connectionPaint;
    private Path path;
    
    private int markerColor;
    private int connectedLinesColor;
    private int guidelinesColor;
    private int graduationColor;
    
    private int graphHeight;
    
    private int weeksCount;
    private int weekWidth;
    
    private int maxXGraduation;
    private int maxYGraduation;
    
    private List<Marker> markers;
    
    public Graph (Context context) {
        super (context);
        init (context, null, 0, 0);
    }
    
    public Graph (Context context, @Nullable AttributeSet attrs) {
        super (context, attrs);
        init (context, attrs, 0, 0);
    }
    
    public Graph (Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super (context, attrs, defStyleAttr);
        init (context, attrs, defStyleAttr, 0);
    }
    
    @RequiresApi (api = Build.VERSION_CODES.LOLLIPOP)
    public Graph (Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super (context, attrs, defStyleAttr, defStyleRes);
        init (context, attrs, defStyleAttr, defStyleRes);
    }
    
    private void init (Context context, AttributeSet attrs, int defStyle, int defStyleRes) {
        paint = new Paint (Paint.ANTI_ALIAS_FLAG);
        path = new Path ();
        
        final TypedArray typedArray = context.obtainStyledAttributes (attrs, R.styleable.Graph, defStyle, defStyleRes);
    
        int defaultColor = getResources ().getColor (R.color.colorPrimary);
        
        markerColor = typedArray.getColor (R.styleable.Graph_markerColor, defaultColor);
        connectedLinesColor = typedArray.getColor (R.styleable.Graph_connectedLinesColor, defaultColor);
        guidelinesColor = typedArray.getColor (R.styleable.Graph_guidelinesColor, defaultColor);
        graduationColor = typedArray.getColor (R.styleable.Graph_graduationColor, defaultColor);
    
        int gradColorStart = typedArray.getColor (R.styleable.Graph_gradColorStart, defaultColor);
        int gradColorEnd = typedArray.getColor (R.styleable.Graph_gradColorEnd, defaultColor);
        LinearGradient gradient = new LinearGradient (
            getPaddingLeft (),
            getPaddingTop (),
            getPaddingRight (),
            getHeight () - getPaddingBottom (),
            new int[] { gradColorStart, gradColorEnd },
            null,
            Shader.TileMode.CLAMP
        );
    
        gradientPaint = new Paint (Paint.ANTI_ALIAS_FLAG);
        gradientPaint.setStyle (Paint.Style.FILL);
        gradientPaint.setShader (gradient);
    
        connectionPaint = new Paint ();
        connectionPaint.setColor (connectedLinesColor);
        connectionPaint.setStrokeWidth (3);
        
        typedArray.recycle ();
    }
    
    @Override
    protected void onDraw (Canvas canvas) {
        super.onDraw (canvas);
        
        if (markers == null) {
            return;
        }
        
        drawSkeleton (canvas);
        drawGraduations (canvas);
        drawConnectPoints (canvas);
        colorAreaBelowPoints (canvas);
    }
    
    private void drawSkeleton (Canvas canvas) {
        // draw Y axis
        weekWidth = (getWidth () - getPaddingLeft () - getPaddingRight ()) / weeksCount;
    
        graphHeight = getHeight () - getPaddingTop () - getPaddingBottom ();
        
        initSkeletonPaint ();
        
        int maxY = getHeight () - getPaddingBottom ();
        int x = getPaddingLeft ();
        
        for (int i = 0; i < weeksCount; i ++) {
            
            path.moveTo (x, getPaddingTop ());
            path.lineTo (x, maxY);
    
            canvas.drawPath (path, paint);
    
            path.reset ();
    
            x += weekWidth;
        }
        
        path.reset ();
        paint.reset ();
    }
    
    private void initSkeletonPaint () {
        paint.setStyle (Paint.Style.STROKE);
        paint.setStrokeWidth (2);
        paint.setColor (guidelinesColor);
        
        float [] interval = new float [graphHeight / 10];
        for (int i = 0; i < interval.length; i ++) {
            interval [i] = 10;
        }
        
        paint.setPathEffect (new DashPathEffect (interval, 0f));
    }
    
    private void drawGraduations (Canvas canvas) {
        initGraduationsPaint ();
        
        int x = getWidth () - getPaddingRight ();
        
        float distY = (100f * graphHeight) / maxYGraduation;
        float y = getHeight () - getPaddingBottom ();
        
        for (int i = 0; i <= maxYGraduation; i += 100) {
            canvas.drawText (String.valueOf (i), x, y, paint);
            
            y -= distY;
        }
        
        path.reset ();
        paint.reset ();
    }
    
    private void initGraduationsPaint () {
        paint.setColor (graduationColor);
        paint.setTextAlign (Paint.Align.LEFT);
        paint.setTextSize (40);
    }
    
    private void drawConnectPoints (Canvas canvas) {
        initPointsPaint ();
        
        float distBetweenPoints = ((float) weekWidth) / 7;
        
        float centerX = getPaddingLeft ();
        
        float prevX = -1f;
        float prevY = -1f;
        for (Marker marker : markers) {
            float centerY = (getHeight () - getPaddingBottom ()) - (marker.getValue () * graphHeight) / maxYGraduation;
            
            if (prevX != -1f) {
                canvas.drawLine (prevX, prevY, centerX, centerY, connectionPaint);
            }
            prevX = centerX;
            prevY = centerY;
            
            canvas.drawCircle (centerX, centerY, 7, paint);
            
            centerX += distBetweenPoints;
        }
        
        paint.reset ();
    }
    
    private void initPointsPaint () {
        paint.setStyle (Paint.Style.FILL);
        paint.setStrokeWidth (5);
        paint.setColor (markerColor);
    }
    
    private void colorAreaBelowPoints (Canvas canvas) {
        path.moveTo (getPaddingLeft (), getHeight () - getPaddingBottom ());
    
        float centerX = getPaddingLeft ();
        float distBetweenPoints = ((float) weekWidth) / 7;
        
        for (Marker marker : markers) {
            float centerY = (getHeight () - getPaddingBottom ()) - (marker.getValue () * graphHeight) / maxYGraduation;
            
            path.lineTo (centerX, centerY);
            
            centerX += distBetweenPoints;
        }
        
        float firstY = (getHeight () - getPaddingBottom ()) - (markers.get (0).getValue () * graphHeight) / maxYGraduation;
        float lastX = centerX - distBetweenPoints;
        path.lineTo (lastX, getHeight () - getPaddingBottom ());
        path.lineTo (getPaddingLeft (), firstY);
        
        canvas.drawPath (path, gradientPaint);
        
        path.reset ();
    }
    
    public void setData (List<Marker> markers) {
        this.markers = markers;
    
        int maxY = maxValue (markers);
    
        maxXGraduation = markers.size () + 1;
        maxYGraduation = ((maxY / 100) + 1) * 100;
        
        for (Marker marker : markers) {
            weeksCount = Math.max (weeksCount, marker.getWeek ());
        }
    
        invalidate ();
    }
    
    private int maxValue (List<Marker> markers) {
        int maxValue = 0;
        
        for (Marker marker : markers) {
            maxValue = Math.max (maxValue, marker.getValue ());
        }
        
        return maxValue;
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {
    
    @Override
    protected void onCreate (Bundle savedInstanceState) {
        super.onCreate (savedInstanceState);
        setContentView (R.layout.activity_main);
        
        Graph graph = findViewById (R.id.graph);
        
        graph.setData (markers ());
    }
    
    private List<Marker> markers () {
        List<Marker> markers = new ArrayList<> ();
        
        markers.add (new Marker (0,     1,  1, 1));
        markers.add (new Marker (200,   2,  1, 1));
        markers.add (new Marker (100,   3,  1, 1));
        markers.add (new Marker (150,   4,  1, 1));
        markers.add (new Marker (50,    5,  1, 1));
        markers.add (new Marker (0,     6,  1, 1));
        markers.add (new Marker (350,   7,  1, 1));
        
        markers.add (new Marker (320,   1,  2, 1));
        markers.add (new Marker (320,   2,  2, 1));
        markers.add (new Marker (275,   3,  2, 1));
        markers.add (new Marker (0,     4,  2, 1));
        markers.add (new Marker (0,     5,  2, 1));
        markers.add (new Marker (200,   6,  2, 1));
        markers.add (new Marker (30,    7,  2, 1));
        
        markers.add (new Marker (550,   1,  3, 1));
        markers.add (new Marker (80,    2,  3, 1));
        markers.add (new Marker (110,   3,  3, 1));
        markers.add (new Marker (50,    4,  3, 1));
        markers.add (new Marker (50,    5,  3, 1));
        markers.add (new Marker (80,    6,  3, 1));
        markers.add (new Marker (50,    7,  3, 1));
        
        markers.add (new Marker (0,     1,  4, 1));
        markers.add (new Marker (30,    2,  4, 1));
        markers.add (new Marker (70,    3,  4, 1));
        markers.add (new Marker (110,   4,  4, 1));
        markers.add (new Marker (70,    5,  4, 1));
        markers.add (new Marker (0,     6,  4, 1));
        markers.add (new Marker (30,    7,  4, 1));
        
        markers.add (new Marker (70,    1,  5, 1));
        markers.add (new Marker (130,   2,  5, 1));
        markers.add (new Marker (250,   3,  5, 1));
        
        return markers;
    }
}

Marker.java

public class Marker {
    
    private int value;
    private int day;
    private int week;
    private int month;
    
    public Marker (int value, int day, int week, int month) {
        this.value = value;
        this.day = day;
        this.week = week;
        this.month = month;
    }
    
    public int getValue () {
        return value;
    }
    
    public void setValue (int value) {
        this.value = value;
    }
    
    public int getDay () {
        return day;
    }
    
    public void setDay (int day) {
        this.day = day;
    }
    
    public int getWeek () {
        return week;
    }
    
    public void setWeek (int week) {
        this.week = week;
    }
    
    public int getMonth () {
        return month;
    }
    
    public void setMonth (int month) {
        this.month = month;
    }
}