Getting file paths of loaded layers in QGIS plugin?

I have solved my problem, thanks to Matt and to this link : http://osgeo-org.1560.x6.nabble.com/Display-raster-layer-on-own-Map-Canvas-td5002935.html

Here is how I do it, inside the [moduleName]2dialog.py file generated by the plugin builder plugin :

from PyQt4 import QtCore, QtGui
from PyQt4.QtCore import QFile, QFileInfo
from qgis import core, gui, utils
from qgis.core import QgsRasterLayer
from qgis.gui import QgsMapCanvasLayer
from qgis.utils import iface

layers = iface.legendInterface().layers()
for each_layer in layers:
    fileName = each_layer
    fileInfo = QFileInfo(fileName)
    baseName = fileInfo.baseName()
    self.layer = QgsRasterLayer(fileName, baseName)

    QgsMapLayerRegistry.instance().addMapLayer(self.layer)
    self.canvas = self.ui.qgsMapCanvas
    self.canvas.setCanvasColor(QtCore.Qt.white)
    self.canvas.setExtent(self.layer.extent())
    self.canvas.setLayerSet( [ QgsMapCanvasLayer(self.layer) ] )
    r = QgsRubberBand(self.ui.qgsMapCanvas, True)
    self.canvas.setCurrentLayer(self.layer)
    self.canvas.setVisible(True)
    self.canvas.refresh()

You can get a list of the layers in the table of contents and perform actions like so:

legend = self.iface.legendInterface()
layers = legend.layers()
for each_layer in layers:
    if each_layer.type() == "RasterLayer":
        print each_layer.id()
        print each_layer.name()