[GIS] How to save and load vector layer attribute value map, editable state in .qml style file

qgisqgis-2.4qmlstyle

I just upgraded to Qgis 2.4 and there were problems with style file:

  • When I load style file for Qgis <= 2.2, the color of features is
    right but when I edit them, the value map (value – description pair)
    is lost.
  • The value map I created for layers in Qgis 2.4 is not
    kept in .qml style file when I choose 'save style' as 'Qgis layer
    style file'.

Is this a bug in Qgis 2.4?

ADDED INFORMATION:

Sample files: http://www.mediafire.com/download/bbk02sj3jl9iwtc/test_data.7z

For line layer line.shp with 3 attributes: id, name, type – I have style file 2_2_line_style.qml generated from Qgis 2.2 which have following lines:

  <edittypes>
    <edittype labelontop="0" editable="0" type="0" name="id"/>
    <edittype labelontop="0" editable="1" type="0" name="name"/>
    <edittype labelontop="0" editable="1" type="3" name="type">
      <valuepair key="first type" value="1"/>
      <valuepair key="second type" value="2"/>
      <valuepair key="third type" value="3"/>
    </edittype>
  </edittypes>

In Qgis 2.2, when I load that line layer with that style and add more lines, there will be a pop up window that allows me to enter values with a drop down list:

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But in Qgis 2.4, when I load the same layer with the style file and add (create new) features, the drop down list is gone:

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More over, in Qgis 2.4, when I set the value map for that line layer manually, I can get the drop down list but when I save the style as .qml and inspect the file, there isn't any key – value line like the 2.2 style file.

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Best Answer

My apologies for the off-the-record answer. For me it seems you have found a bug :-)

I can reproduce your problem and did not find a solution/explanation for it...

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Before ADDED INFORMATION

Strange, but I don't think it's a bug. In QGIS 2.4 I loaded a vector layer, applied a style by loading a .qml saved in QGIS 2.2, and there were no issues. I made a small change in the value map, saved it as a new .qml and loading it again went smoothly.

If you mention '... when I edit them', do you mean you select another color range from the dropdown menu? Because that's perfectly possible without losing your value-description settings. Just don't click 'Classify' because that will mess up your value map according to the classification mode you selected. But I guess you know all that...

Opening a .qml file in Notepad, you normally should see your value map at the top. Something like: 

<ranges>
  <range symbol="0" lower="0.000000" upper="12000.000000" label="No data"/>
  <range symbol="1" lower="12000.000000" upper="16000.000000" label="12000 - 16000"/>
  <range symbol="2" lower="16000.000000" upper="21000.000000" label="16000 - 21000"/>
  <range symbol="3" lower="21000.000000" upper="25000.000000" label="21000 - 25000"/>
  <range symbol="4" lower="25000.000000" upper="29000.000000" label="25000 - 29000"/>
</ranges>

After your comment, this will probably help you further.

IF I understand what you're doing, you try to edit the values map under the Fields tab, and there you find a column called 'Edit Widget'.

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I did not dig out that functionality yet, but assuming you just want to apply a style on a vector layer (nice colors and dito labels), open the Properties window of the vector layer you like to apply a style on, and do as follows.

  • If you already have a .qml file, you can load it through 'Load Style ...' (A).

  • Check out that the name of the attribute/field (stored in the .qml file) corresponds with an existing attribute in the table of your vector layer. If not, just select from the dropdown menu the column/field/attribute you like to show in your map with your style (B). In the .qml file, you can find the attribute's name in the 3th line:

    <renderer-v2 attr="FIELD_OF_INTEREST" symbollevels="1" type="graduatedSymbol">

  • If you're still happy with the style you loaded, fine! If not, edit the number of classes, choose a color ramp and a classification mode. If you're not satisfied with the lower and upper values of the generated classes, double-click in the area depicted with the red rectangle (C).

  • A small window opens allowing you to adapt the lower and upper values to your wishes (D).
  • Finally, you can edit the description of your classes (E). In this example you see the value map of a numerical field, but in case of, for example, a land use map, your value can be an integer code and the description the name of the corresponding land use.
  • Click 'OK' to apply the configured style (maybe you can save your style first with 'Save Style').

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All done, you'll notice that the applied changes (color and value map) will appear as a legend.

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