adding back, open and file chooser button.

main/ui/src/main/java/org/cryptomator/ui/addvaultwizard/ChooseExistingVaultController.java

@@ -1,13 +1,43 @@
 package org.cryptomator.ui.addvaultwizard;
 
+import javafx.event.ActionEvent;
+import javafx.stage.FileChooser;
+import javafx.stage.Stage;
+import org.cryptomator.ui.common.FXMLLoaderFactory;
 import org.cryptomator.ui.common.FxController;
 
 import javax.inject.Inject;
+import java.io.File;
+import java.io.IOException;
 
 @AddVaultWizardScoped
 public class ChooseExistingVaultController implements FxController {
 
+	private final FXMLLoaderFactory fxmlLoaders;
+	private final Stage window;
+
 	@Inject
-	ChooseExistingVaultController() {}
+	ChooseExistingVaultController(@AddVaultWizard Stage window, @AddVaultWizard FXMLLoaderFactory fxmlLoaders) {
+		this.window = window;
+		this.fxmlLoaders = fxmlLoaders;
+	}
+
+	public void chooseFile(ActionEvent actionEvent) {
+		FileChooser fileChooser = new FileChooser();
+		fileChooser.setTitle("Open Masterkey File");
+		fileChooser.getExtensionFilters().add(new FileChooser.ExtensionFilter("Cryptomator Masterkey", "*.cryptomator"));
+		final File file = fileChooser.showOpenDialog(window);
+		if (file != null) {
+			window.setWidth(100);
+		}
+	}
+
+	public void goBack(ActionEvent actionEvent) throws IOException {
+		fxmlLoaders.setScene("/fxml/addvault_welcome.fxml", window);
+
+	}
 
+	public void confirm(ActionEvent actionEvent) {
+		window.close();
+	}
 }

main/ui/src/main/resources/fxml/addvault_existing.fxml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
 <?import javafx.geometry.Insets?>
+<?import javafx.scene.control.Button?>
 <?import javafx.scene.control.Label?>
 <?import javafx.scene.layout.VBox?>
 <VBox xmlns="http://javafx.com/javafx"
@@ -13,6 +14,9 @@
 		<Insets top="12" right="12" bottom="12" left="12"/>
 	</padding>
 	<children>
-		<Label text="TODO existing!"/>
+		<Label text="Open your existing vault by choosing its masterkey file:"/>
+		<Button text="file picker" onAction="#chooseFile"/>
+		<Button text="Back" onAction="#goBack"/>
+		<Button text="Open" onAction="#confirm"/>
 	</children>
 </VBox>