Since nobody helped me any trick, I tried to overide DateAxis to get Axis with tick labels alignment. I named it 'AlignedDateAxis'. It extends DateAxis and overrides only methods that are used for tick labels rendering. It can render tick labels in two ways: in standard way that places labels under ticks, and in required way that centers labels in the middle of interval.
Because I don't know much about JFreeCharts library understanding some classes and methods wasn't easy for me. I hope it will work fine in all common cases.
My class contains javadoc and comments only in my native language, so I won't post them complete here.
package x.y.z;
import java.awt.Graphics2D;
import java.awt.Shape;
import java.awt.geom.Line2D;
import java.awt.geom.Rectangle2D;
import java.util.Date;
import java.util.List;
import org.jfree.chart.axis.AxisState;
import org.jfree.chart.axis.DateAxis;
import org.jfree.chart.axis.DateTick;
import org.jfree.chart.axis.DateTickUnit;
import org.jfree.chart.axis.TickType;
import org.jfree.chart.axis.ValueTick;
import org.jfree.text.TextUtilities;
import org.jfree.ui.RectangleEdge;
/**
* Extension of DateAxis for jFreeChart graphs that can render tick labels in two ways:
* 1) labels under ticks (common way, same as DateAxis)
* 2) labels in the middle of interval (new feature)
* @author Honza Spurny, Czech Republic
* @version 1.0
*/
public class AlignedDateAxis extends DateAxis {
/**
* Tick labels alignment setting.
*/
private TickLabelPosition tickLabelPosition = TickLabelPosition.DEFAULT_VALUE;
/**
* Value for interface Serializable.
*/
static private final long serialVersionUID = 1;
// ***********************
// *** Enums ***
// ***********************
/**
* Tick label alignment modes.
*/
public enum TickLabelPosition {
/**
* Tick label is rendered under/next by own tick.
* (common rendering same as in DateAxis)
*/
INTERVAL_START,
/**
* Tick label is placed in the middle of interval
* (between two subsequent ticks)
*/
INTERVAL_MIDDLE;
static public final TickLabelPosition DEFAULT_VALUE = INTERVAL_START;
}
// ******************************
// *** Constructors ***
// ******************************
/**
* Default constructor.
*/
public AlignedDateAxis() {
super();
}
/**
* Constructor.
* @param tickLabelPos tick label alignment mode setting for this axis.
*/
public AlignedDateAxis(TickLabelPosition tickLabelPos) {
this();
this.setTickLabelPosition(tickLabelPos);
}
// *********************************
// *** GET/SET methods ***
// *********************************
public TickLabelPosition getTickLabelPosition() {
return this.tickLabelPosition;
}
public void setTickLabelPosition(TickLabelPosition value) {
this.tickLabelPosition = value;
}
// *******************************************************
// *** Overrided methods for label rendering ***
// *******************************************************
/**
* Auxiliary method to calculate tick label position of given tick.
* @param tick tick we need calculate label position for (DateTick is expected)
* @param cursor the cursor
* @param dataArea area to draw the ticks and labels in
* @param edge edge of dataArea
* @return Returns coordinates [x,y] where label should be placed.
*/
@Override
protected float[] calculateAnchorPoint(ValueTick tick, double cursor, Rectangle2D dataArea, RectangleEdge edge) {
float[] resultAnchor = super.calculateAnchorPoint(tick, cursor, dataArea, edge);
// Time of tick
Date tickDate = (tick instanceof DateTick) ?
((DateTick) tick).getDate() :
new Date((long)tick.getValue());
// Tick label shift.
// (for INTERVAL_START it is 0, for INTERVAL_MIDDLE it is calculated)
double labelShift;
switch (this.getTickLabelPosition()) {
case INTERVAL_MIDDLE:
// Getting next tick value...
DateTickUnit unit = this.getTickUnit();
Date nextTickDate = unit.addToDate(tickDate, this.getTimeZone());
double nextTickVal = this.valueToJava2D(nextTickDate.getTime(), dataArea, edge);
// Shifting label in between ticks...
labelShift = (nextTickVal - resultAnchor[0]) / 2;
break;
case INTERVAL_START:
default:
labelShift = 0;
break;
}
// Edge defines which coordinate is shifted.
if (RectangleEdge.isTopOrBottom(edge)) {
resultAnchor[0] += labelShift;
} else if (RectangleEdge.isLeftOrRight(edge)) {
resultAnchor[1] += labelShift;
}
return resultAnchor;
}
/**
* Renders this axis with ticks and labels.
* @param g2 graphics to draw the axis in.
* @param cursor the cursor
* @param plotArea area to draw the chart in
* @param dataArea area to draw this axis in
* @param edge edge of dataArea
* @return Returns state of axis.
*/
@Override
protected AxisState drawTickMarksAndLabels(Graphics2D g2, double cursor, Rectangle2D plotArea, Rectangle2D dataArea, RectangleEdge edge) {
AxisState state = new AxisState(cursor);
if (this.isAxisLineVisible()) this.drawAxisLine(g2, cursor, dataArea, edge);
List<DateTick> ticks = this.refreshTicks(g2, state, dataArea, edge);
state.setTicks(ticks);
g2.setFont(this.getTickLabelFont());
for (DateTick tick: ticks) {
if (this.isTickLabelsVisible()) {
g2.setPaint(this.getTickLabelPaint());
float anchorPoint[] = this.calculateAnchorPoint(tick, cursor, dataArea, edge);
// TextUtilities.drawRotatedString(tick.getText(), g2, anchorPoint[0], anchorPoint[1], tick.getTextAnchor(), tick.getAngle(), tick.getRotationAnchor());
// Commented code above is original code from DateAxis.
// ---[Override]---
// Position of tick label is shifted so it can point outside the dataArea.
// We have to check whether the tick label on this position is drawable into the given area.
Shape labelBounds = TextUtilities.calculateRotatedStringBounds(tick.getText(), g2, anchorPoint[0], anchorPoint[1], tick.getTextAnchor(), tick.getAngle(), tick.getRotationAnchor());
double labelEdge = (RectangleEdge.isTopOrBottom(edge)) ? (labelBounds.getBounds2D().getMaxX()) : (labelBounds.getBounds2D().getMaxY());
double dataAreaBound = (RectangleEdge.isTopOrBottom(edge)) ? (dataArea.getMaxX()) : (dataArea.getMaxY());
// Magic constant 5: tick label can be rendered although it exceeds area edge for max. 5px
// (it still looks good - visualy tested :-)
if ((labelEdge - 5) <= dataAreaBound) {
TextUtilities.drawRotatedString(tick.getText(), g2, anchorPoint[0], anchorPoint[1], tick.getTextAnchor(), tick.getAngle(), tick.getRotationAnchor());
}
// ---[/Override]---
}
if ( (this.isTickMarksVisible() && tick.getTickType().equals(TickType.MAJOR)) || (this.isMinorTickMarksVisible() && tick.getTickType().equals(TickType.MINOR)) ) {
double ol = tick.getTickType().equals(TickType.MINOR) ? this.getMinorTickMarkOutsideLength() : this.getTickMarkOutsideLength();
double il = tick.getTickType().equals(TickType.MINOR) ? this.getMinorTickMarkInsideLength() : this.getTickMarkInsideLength();
float tickVal = (float)this.valueToJava2D(tick.getValue(), dataArea, edge);
Line2D mark = null;
g2.setStroke(this.getTickMarkStroke());
g2.setPaint(this.getTickMarkPaint());
if(edge == RectangleEdge.LEFT) {
mark = new Line2D.Double(cursor - ol, tickVal, cursor + il, tickVal);
} else if(edge == RectangleEdge.RIGHT) {
mark = new Line2D.Double(cursor + ol, tickVal, cursor - il, tickVal);
} else if(edge == RectangleEdge.TOP) {
mark = new Line2D.Double(tickVal, cursor - ol, tickVal, cursor + il);
} else if(edge == RectangleEdge.BOTTOM) {
mark = new Line2D.Double(tickVal, cursor + ol, tickVal, cursor - il);
}
g2.draw(mark);
}
}
if (this. isTickLabelsVisible()) {
double used = 0.0;
if (edge == RectangleEdge.LEFT) {
used += this.findMaximumTickLabelWidth(ticks, g2, plotArea, this.isVerticalTickLabels());
state.cursorLeft(used);
} else if (edge == RectangleEdge.RIGHT) {
used = this.findMaximumTickLabelWidth(ticks, g2, plotArea, this.isVerticalTickLabels());
state.cursorRight(used);
} else if (edge == RectangleEdge.TOP) {
used = this.findMaximumTickLabelHeight(ticks, g2, plotArea, this.isVerticalTickLabels());
state.cursorUp(used);
} else if (edge == RectangleEdge.BOTTOM) {
used = this.findMaximumTickLabelHeight(ticks, g2, plotArea, this.isVerticalTickLabels());
state.cursorDown(used);
}
}
return state;
}
}
This axis-class (AlignedDateAxis) works fine for me and I'm using it in my project.
Honza (sporak)
PeriodAxisworks out, you can answer your own question. – Apulia