Support replacing existing keystore with watch only keystore

src/main/java/com/sparrowwallet/sparrow/keystoreimport/KeystoreImportDialog.java

@@ -1,17 +1,16 @@
 package com.sparrowwallet.sparrow.keystoreimport;
 
 import com.google.common.eventbus.Subscribe;
+import com.sparrowwallet.drongo.KeyDerivation;
 import com.sparrowwallet.drongo.wallet.Keystore;
 import com.sparrowwallet.drongo.wallet.KeystoreSource;
 import com.sparrowwallet.drongo.wallet.Wallet;
+import com.sparrowwallet.drongo.wallet.WalletModel;
 import com.sparrowwallet.sparrow.AppController;
 import com.sparrowwallet.sparrow.EventManager;
 import com.sparrowwallet.sparrow.event.KeystoreImportEvent;
 import javafx.fxml.FXMLLoader;
-import javafx.scene.control.ButtonBar;
+import javafx.scene.control.*;
-import javafx.scene.control.ButtonType;
-import javafx.scene.control.Dialog;
-import javafx.scene.control.DialogPane;
 import org.controlsfx.tools.Borders;
 
 import java.io.IOException;
@@ -41,12 +40,13 @@ public class KeystoreImportDialog extends Dialog<Keystore> {
             keystoreImportController.initializeView(wallet);
             keystoreImportController.selectSource(initialSource);
 
+            final ButtonType watchOnlyButtonType = new javafx.scene.control.ButtonType("xPub / Watch Only Wallet", ButtonBar.ButtonData.LEFT);
             final ButtonType cancelButtonType = new javafx.scene.control.ButtonType("Cancel", ButtonBar.ButtonData.CANCEL_CLOSE);
-            dialogPane.getButtonTypes().addAll(cancelButtonType);
+            dialogPane.getButtonTypes().addAll(watchOnlyButtonType, cancelButtonType);
             dialogPane.setPrefWidth(650);
             dialogPane.setPrefHeight(620);
 
-            setResultConverter(dialogButton -> dialogButton != cancelButtonType ? keystore : null);
+            setResultConverter(dialogButton -> dialogButton != cancelButtonType ? getWatchOnlyKeystore() : null);
         } catch(IOException e) {
             throw new RuntimeException(e);
         }
@@ -56,6 +56,14 @@ public class KeystoreImportDialog extends Dialog<Keystore> {
         return List.of(KeystoreSource.HW_USB, KeystoreSource.HW_AIRGAPPED, KeystoreSource.SW_SEED);
     }
 
+    private Keystore getWatchOnlyKeystore() {
+        this.keystore = new Keystore();
+        keystore.setSource(KeystoreSource.SW_WATCH);
+        keystore.setWalletModel(WalletModel.SPARROW);
+        keystore.setKeyDerivation(new KeyDerivation("",""));
+        return keystore;
+    }
+
     @Subscribe
     public void keystoreImported(KeystoreImportEvent event) {
         this.keystore = event.getKeystore();

src/main/java/com/sparrowwallet/sparrow/wallet/KeystoreController.java

@@ -259,7 +259,12 @@ public class KeystoreController extends WalletFormController implements Initiali
             label.setText(keystore.getLabel());
             fingerprint.setText(keystore.getKeyDerivation().getMasterFingerprint());
             derivation.setText(keystore.getKeyDerivation().getDerivationPath());
+
+            if(keystore.getExtendedPublicKey() != null) {
                 xpub.setText(keystore.getExtendedPublicKey().toString());
+            } else {
+                xpub.setText("");
+            }
         }
     }
 

src/main/resources/com/sparrowwallet/sparrow/wallet/keystore.fxml

@@ -13,6 +13,7 @@
 <?import org.controlsfx.control.SegmentedButton?>
 <?import com.sparrowwallet.drongo.wallet.KeystoreSource?>
 <?import org.controlsfx.glyphfont.Glyph?>
+<?import com.sparrowwallet.sparrow.control.HelpLabel?>
 <StackPane stylesheets="@keystore.css, @settings.css, @../general.css" xmlns="http://javafx.com/javafx/10.0.2-internal" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.sparrowwallet.sparrow.wallet.KeystoreController">
     <padding>
         <Insets left="25.0" right="25.0" />
@@ -40,7 +41,7 @@
                 <TextField fx:id="label" maxWidth="160"/>
             </Field>
             <Field text="Master fingerprint:">
-                <TextField fx:id="fingerprint" maxWidth="80" promptText="ffffffff"/>
+                <TextField fx:id="fingerprint" maxWidth="80" promptText="ffffffff"/> <HelpLabel helpText="A master fingerprint is the first 4 bytes of the master public key hash. It is safe to use any valid value (ffffffff) for Watch Only Wallets." />
             </Field>
             <Field text="Derivation:">
                 <TextField fx:id="derivation" maxWidth="200"/>
@@ -80,7 +81,7 @@
                         <KeystoreSource fx:constant="SW_SEED"/>
                     </userData>
                 </ToggleButton>
-                <ToggleButton text="XPUB / Watch Only Wallet" contentDisplay="TOP" wrapText="true" textAlignment="CENTER" toggleGroup="$keystoreSourceToggleGroup" onAction="#selectSource">
+                <ToggleButton text="xPub / Watch Only Wallet" contentDisplay="TOP" wrapText="true" textAlignment="CENTER" toggleGroup="$keystoreSourceToggleGroup" onAction="#selectSource">
                     <graphic>
                         <Glyph fontFamily="Font Awesome 5 Free Solid" fontSize="20" icon="EYE" />
                     </graphic>