Как получить GWTUpload SingleUploader для замены ранее выбранного изображения

Question

Я использую GWTUpload SingleUploader для выбора и отображения фотографии. Если я выберу фотографию, а затем передумаю и выберем другую фотографию, следующая фотография будет показана рядом с первой. Как мне его заменить, чтобы заменить предыдущую фотографию.

С уважением,

Глин

package org.AwardTracker.client; 

import com.google.gwt.user.client.Window; 
import com.google.gwt.user.client.ui.Composite; 
import com.google.gwt.user.client.ui.FlowPanel; 
import com.google.gwt.user.client.ui.VerticalPanel; 
import com.google.gwt.user.client.ui.Label; 
import com.google.gwt.user.client.ui.FlexTable; 
import com.google.gwt.user.client.ui.TextBox; 
import com.google.gwt.user.client.ui.Button; 
import com.google.gwt.core.client.GWT; 
import com.google.gwt.event.dom.client.ClickHandler; 
import com.google.gwt.event.dom.client.ClickEvent; 
import com.google.gwt.user.client.rpc.AsyncCallback; 
import com.google.gwt.user.client.rpc.ServiceDefTarget; 
import com.google.gwt.user.client.ui.HorizontalPanel; 
import com.google.gwt.user.client.ui.Image; 
import com.google.gwt.user.client.ui.HasHorizontalAlignment; 
import com.google.gwt.user.client.ui.ListBox; 
import com.google.gwt.i18n.client.DateTimeFormat; 

import gwtupload.client.IFileInput; 
import gwtupload.client.IFileInput.FileInputType; 
import gwtupload.client.IUploadStatus.Status; 
import gwtupload.client.IUploader; 
import gwtupload.client.IUploader.UploadedInfo; 
import gwtupload.client.MultiUploader; 
import gwtupload.client.PreloadedImage; 
import gwtupload.client.PreloadedImage.OnLoadPreloadedImageHandler; 
import gwtupload.client.SingleUploader; 

//import java.awt.image.BufferedImage; 
import java.io.File; 
import java.lang.String; 
import java.sql.Date; 
import java.util.List; 

import com.google.gwt.user.client.ui.FileUpload; 
import com.google.gwt.user.datepicker.client.DateBox; 
import com.google.gwt.user.datepicker.client.DateBox.DefaultFormat; 

public class EditYouthMemberView extends Composite { 

private DBConnectionAsync rpc; 
private TextBox textBoxFirstName; 
private TextBox textBoxScoutNumber; 
private ListBox listBoxSection; 
private ListBox listBoxPack; 
private TextBox textBoxSurname; 
private DateBox dateBoxArchived; 
private DateBox dateBoxPackIn; 
private DateBox dateBoxPackOut; 
private DateBox dateBoxDOB; 
// A panel where the thumbnails of upload images will be shown 
//final FlowPanel panelImages = new FlowPanel(); 
final HorizontalPanel panelImages = new HorizontalPanel(); 


@SuppressWarnings("deprecation") 
public EditYouthMemberView(final NavHandler navHandler) {  

    final java.util.Date todays_date = new java.util.Date(); 

    rpc = (DBConnectionAsync) GWT.create(DBConnection.class); 
    ServiceDefTarget target = (ServiceDefTarget) rpc; 
    String moduleRelativeURL = GWT.getModuleBaseURL() + "MySQLConnection"; 
    target.setServiceEntryPoint(moduleRelativeURL); 

    VerticalPanel verticalPanel = new VerticalPanel(); 
    verticalPanel.setStyleName("gwt-Banner"); 
    initWidget(verticalPanel); 

    HorizontalPanel horizontalPanel = new HorizontalPanel(); 
    horizontalPanel.setStyleName("gwt-Banner"); 
    verticalPanel.add(horizontalPanel); 
    horizontalPanel.setWidth("246px"); 

    Label lblHome = new Label("Home"); 
    lblHome.addClickHandler(new ClickHandler() { 
     public void onClick(ClickEvent event) { 
     } 
    }); 
    horizontalPanel.add(lblHome); 
    lblHome.setWidth("46px"); 

    Label lblEditAwards = new Label("Edit Awards"); 
    lblEditAwards.addClickHandler(new ClickHandler() { 
     public void onClick(ClickEvent event) { 
     } 
    }); 
    horizontalPanel.add(lblEditAwards); 
    lblEditAwards.setWidth("85px"); 

    Label lblListAll = new Label("List all Cub Scouts"); 
    lblListAll.addClickHandler(new ClickHandler() { 
     public void onClick(ClickEvent event) { 
     } 
    }); 
    horizontalPanel.add(lblListAll); 
    lblListAll.setWidth("130px"); 

    Label lblAccountUpdate = new Label("Account Update"); 
    lblAccountUpdate.addClickHandler(new ClickHandler() { 
     public void onClick(ClickEvent event) { 
     } 
    }); 
    horizontalPanel.add(lblAccountUpdate); 
    lblAccountUpdate.setWidth("104px"); 

    FlexTable flexTable_1 = new FlexTable(); 
    verticalPanel.add(flexTable_1); 

    Label lblSurname = new Label("Surname"); 
    lblSurname.setWordWrap(false); 
    lblSurname.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_LEFT); 
    lblSurname.setStyleName("gwt-Label-Login"); 
    flexTable_1.setWidget(0, 2, lblSurname); 

    Label lblFirstName = new Label("First Name"); 
    lblFirstName.setWordWrap(false); 
    lblFirstName.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_LEFT); 
    lblFirstName.setStyleName("gwt-Label-Login"); 
    flexTable_1.setWidget(0, 3, lblFirstName); 

    textBoxSurname = new TextBox(); 
    flexTable_1.setWidget(1, 1, textBoxSurname); 

    textBoxFirstName = new TextBox(); 
    flexTable_1.setWidget(1, 2, textBoxFirstName);  

    Label lblLookForPhotograph = new Label("Look for photograph:"); 
    lblLookForPhotograph.setWordWrap(false); 
    lblLookForPhotograph.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_LEFT); 
    lblLookForPhotograph.setStyleName("gwt-Label-Login"); 
    flexTable_1.setWidget(2, 1, lblLookForPhotograph); 
    flexTable_1.getFlexCellFormatter().setRowSpan(2, 1, 3); 

    // Attach the image viewer to the document 
    flexTable_1.setWidget(0, 0, panelImages); 
    panelImages.setSize("120", "120"); 
    flexTable_1.getFlexCellFormatter().setRowSpan(0, 0, 4); 
    panelImages.clear(); 

    // Create a new uploader panel and attach it to a document 
    //final SingleUploader defaultUploader = new SingleUploader(IFileInput.FileInputType.LABEL, null); 
    final SingleUploader defaultUploader = new SingleUploader(); 
    defaultUploader.setAutoSubmit(false); 
    defaultUploader.setValidExtensions("jpg"); 
    defaultUploader.setEnabled(true); 

    // Add a finish handler which will load the image once the upload finishes 
    defaultUploader.addOnFinishUploadHandler(onFinishUploaderHandler); 
    defaultUploader.getFileInput().getWidget().setStyleName("customButton"); 
    defaultUploader.getFileInput().getWidget().setSize("159px", "27px"); 
    defaultUploader.avoidRepeatFiles(true); 
    //defaultUploader.setServletPath(defaultUploader.getServletPath() + "?caseId=" + caseObj.getId().toString()); 

    flexTable_1.setWidget(3, 1, defaultUploader); 
    flexTable_1.getFlexCellFormatter().setRowSpan(3, 1, 3); 

    FlexTable flexTable = new FlexTable(); 
    verticalPanel.add(flexTable); 

    Label lblDOB = new Label("Date of Birth:"); 
    lblDOB.setWordWrap(false); 
    lblDOB.setStyleName("gwt-Label-Login"); 
    flexTable.setWidget(0, 0, lblDOB); 
    lblDOB.setDirectionEstimator(false); 
    lblDOB.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_RIGHT); 
    lblDOB.setSize("110px", "16px"); 

    dateBoxDOB = new DateBox(); 
    dateBoxDOB.setFormat(new DefaultFormat(DateTimeFormat.getFormat("dd-MM-yyyy"))); 
    flexTable.setWidget(0, 1, dateBoxDOB); 
    dateBoxDOB.getDatePicker(); 

    Label lblSection = new Label("Section:"); 
    lblSection.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_RIGHT); 
    lblSection.setStyleName("gwt-Label-Login"); 
    flexTable.setWidget(0, 2, lblSection); 

    listBoxSection = new ListBox(); 
    listBoxSection.addItem("Cubs"); 
    flexTable.setWidget(0, 3, listBoxSection); 
    listBoxSection.setVisibleItemCount(1); 

    Label lblScoutNumber = new Label("Scout Number:"); 
    lblScoutNumber.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_RIGHT); 
    lblScoutNumber.setStyleName("gwt-Label-Login"); 
    flexTable.setWidget(1, 0, lblScoutNumber); 
    lblScoutNumber.setDirectionEstimator(false); 
    lblScoutNumber.setSize("110px", "16px"); 

    textBoxScoutNumber = new TextBox(); 
    flexTable.setWidget(1, 1, textBoxScoutNumber); 

    Label lblPack = new Label("Pack:"); 
    lblPack.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_RIGHT); 
    lblPack.setStyleName("gwt-Label-Login"); 
    flexTable.setWidget(1, 2, lblPack); 

    listBoxPack = new ListBox(); 
    listBoxPack.addItem("Explorer"); 
    listBoxPack.addItem("Pioneer"); 
    flexTable.setWidget(1, 3, listBoxPack); 
    listBoxPack.setVisibleItemCount(1); 

    Label lblDateArchived = new Label("Date Archived:"); 
    lblDateArchived.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_RIGHT); 
    lblDateArchived.setStyleName("gwt-Label-Login"); 
    flexTable.setWidget(2, 0, lblDateArchived); 
    lblDateArchived.setSize("110px", "16px"); 

    dateBoxArchived = new DateBox(); 
    dateBoxArchived.setFormat(new DefaultFormat(DateTimeFormat.getFormat("dd-MM-yyyy"))); 
    flexTable.setWidget(2, 1, dateBoxArchived); 
    dateBoxArchived.getDatePicker(); 

    Label lblIn_1 = new Label("In:"); 
    lblIn_1.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_RIGHT); 
    lblIn_1.setStyleName("gwt-Label-Login"); 
    flexTable.setWidget(2, 2, lblIn_1); 

    dateBoxPackIn = new DateBox(); 
    dateBoxPackIn.setFormat(new DefaultFormat(DateTimeFormat.getFullDateFormat())); 
    flexTable.setWidget(2, 3, dateBoxPackIn); 
    dateBoxPackIn.getDatePicker(); 

    Label lblNewLabel_3 = new Label("Out:"); 
    lblNewLabel_3.setStyleName("gwt-Label-Login"); 
    flexTable.setWidget(2, 4, lblNewLabel_3); 

    dateBoxPackOut = new DateBox(); 
    dateBoxPackOut.setFormat(new DefaultFormat(DateTimeFormat.getFormat("dd-MM-yyyy"))); 
    dateBoxPackOut.getDatePicker(); 

    flexTable.setWidget(2, 5, dateBoxPackOut); 

    Button btnAdd = new Button("Add"); 
    btnAdd.addClickHandler(new ClickHandler() { 
     public void onClick(ClickEvent event) { 
      Integer tracker = 0; 
      if (textBoxSurname.getText().length() == 0) { 
       tracker = tracker + 1; 
      } 
      if (textBoxFirstName.getText().length() == 0) { 
       tracker = tracker + 2; 
      } 
      //TO DO 
      // How do I check that a picture has been selected? 
      // if (panelImages.getFilename().length() == 0) { 
      // tracker = tracker + 4; 
      // } 
      if (dateBoxDOB.toString().length() == 0) { 
       tracker = tracker + 8; 
      } 
      if (dateBoxPackIn.toString().length() == 0) { 
       tracker = tracker + 16; 
      } 

      if (tracker == 1) { 
       Window.alert("Please enter a Surname."); 
      } 
      if (tracker == 2) { 
       Window.alert("Please enter a First Name."); 
      } 
      if (tracker == 3) { 
       Window.alert("Please enter Surname and First Name"); 
      } 
      if (tracker == 4) { 
       Window.alert("Please select a photograph."); 
      } 
      if (tracker == 5) { 
       Window.alert("Please enter a Surname and select a photograph."); 
      } 
      if (tracker == 6) { 
       Window.alert("Please enter a FirstName and select a photograph."); 
      } 
      if (tracker == 7) { 
       Window.alert("Please enter Surname, First Name and select a photograph"); 
      } 
      if (tracker == 8) { 
       Window.alert("Please enter a DOB"); 
      } 
      if (tracker == 9) { 
       Window.alert("Please enter a Surname and DOB"); 
      } 
      if (tracker == 10) { 
       Window.alert("Please enter a First Name and DOB"); 
      } 
      if (tracker == 11) { 
       Window.alert("Please enter a Surname, First Name and DOB"); 
      } 
      if (tracker == 12) { 
       Window.alert("Please select a photograph and enter a BOB"); 
      } 
      if (tracker == 13) { 
       Window.alert("Please enter a Surname, select a photograph and enter a DOB"); 
      } 
      if (tracker == 14) { 
       Window.alert("Please enter a FirstName, select a photograph and enter a DOB"); 
      } 
      if (tracker == 15) { 
       Window.alert("Please enter Surname, First Name, select a photograph and enter a DOB"); 
      } 
      if (tracker == 16) { 
       Window.alert("Please enter date joined Pack"); 
      } 

      if (tracker == 17) { 
       Window.alert("Please enter a Surname and date joined Pack."); 
      } 
      if (tracker == 18) { 
       Window.alert("Please enter a First Name and date joined Pack."); 
      } 
      if (tracker == 19) { 
       Window.alert("Please enter Surname, First Name and date joined Pack"); 
      } 
      if (tracker == 20) { 
       Window.alert("Please select a photograph and enter date joined Pack."); 
      } 
      if (tracker == 21) { 
       Window.alert("Please enter a Surname, select a photograph and enter date joined Pack."); 
      } 
      if (tracker == 22) { 
       Window.alert("Please enter a First Name, select a photograph and enter date joined Pack."); 
      } 
      if (tracker == 23) { 
       Window.alert("Please enter Surname, First Name, select a photograph and enter date joined Pack"); 
      } 
      if (tracker == 24) { 
       Window.alert("Please enter a DOB and date joined Pack"); 
      } 
      if (tracker == 25) { 
       Window.alert("Please enter a Surname, DOB and date joined Pack"); 
      } 
      if (tracker == 26) { 
       Window.alert("Please enter a First Name, DOB and date joined Pack"); 
      } 
      if (tracker == 27) { 
       Window.alert("Please enter a Surname, First Name, DOB and date joined Pack"); 
      } 
      if (tracker == 28) { 
       Window.alert("Please select a photograph, enter a BOB and date joined Pack"); 
      } 
      if (tracker == 29) { 
       Window.alert("Please enter a Surname, select a photograph, enter a DOB and date joined Pack"); 
      } 
      if (tracker == 30) { 
       Window.alert("Please enter a FirstName, select a photograph, enter a DOB and date joined Pack"); 
      } 
      if (tracker == 31) { 
       Window.alert("Please enter Surname, First Name, select a photograph, enter a DOB and date joined Pack"); 
      } 

      //if (tracker == 0) { 
      // AsyncCallback<YthMmbrSectDtls> callback = new CreationHandler<YthMmbrSectDtls>(null); 
      // rpc.createYouthMember(null, textBoxSurname.getText(), textBoxFirstName.getText(), dateBoxDOB.getValue(), 
      //   fileUpload.getFilename(), dateBoxArchived.getValue(), null, listBoxSection.getItemText(listBoxSection.getSelectedIndex()), 
      //   listBoxPack.getItemText(listBoxPack.getSelectedIndex()), dateBoxPackIn.getValue(), 
      //   dateBoxPackOut.getValue(), callback); 
      //} 

     } 

    }); 
    flexTable.setWidget(3, 0, btnAdd); 

    Button btnUpdate = new Button("Update"); 
    btnUpdate.addClickHandler(new ClickHandler() { 
     public void onClick(ClickEvent event) { 
     } 
    }); 
    btnUpdate.setText("Update"); 
    flexTable.setWidget(3, 1, btnUpdate); 

    Button btnCancel = new Button("Cancel"); 
    btnCancel.addClickHandler(new ClickHandler() { 
     public void onClick(ClickEvent event) { 
     } 
    }); 
    btnCancel.setText("Cancel"); 
    flexTable.setWidget(3, 2, btnCancel); 

    Button btnClearPage = new Button("Clear Page"); 
    btnClearPage.setText("Clear Page"); 
    btnClearPage.addClickHandler(new ClickHandler() { 
     public void onClick(ClickEvent event) { 
      textBoxSurname.setText(""); 
      textBoxFirstName.setText(""); 
      dateBoxDOB.setValue(null); 
      dateBoxPackIn.setValue(todays_date); 
      dateBoxPackOut.setValue(null); 
      textBoxScoutNumber.setText(""); 
      dateBoxArchived.setValue(null); 
     } 
    }); 
    flexTable.setWidget(3, 3, btnClearPage); 
    setStyleName("body"); 
} 

// Load the image in the document and in the case of success attach it to the viewer 
private IUploader.OnFinishUploaderHandler onFinishUploaderHandler = new IUploader.OnFinishUploaderHandler() { 
    public void onFinish(IUploader uploader) { 
     if (uploader.getStatus() == Status.SUCCESS) { 
      new PreloadedImage(uploader.fileUrl(), showImage); 

      //The server sends useful information to the client by default 
      UploadedInfo info = uploader.getServerInfo(); 
      System.out.println("File name " + info.name); 
      System.out.println("File content-type " + info.ctype); 
      System.out.println("File size " + info.size); 

      // You can send any customised message and parse it 
      System.out.println("Server message " + info.message); 

     } 
    } 
}; 

// Attach an image to the pictures viewer 
private OnLoadPreloadedImageHandler showImage = new OnLoadPreloadedImageHandler() { 
    public void onLoad(PreloadedImage image) { 
     image.setWidth("75px"); 
     panelImages.add(image); 
    } 
}; 

/** 
* Decodes the base64 string into byte array to display image 
* Calls Base64Decode.java 
* @param imageDataString - a {@link java.lang.String} 
* @return byte array 
*/ 
public static byte[] decodeImage(String imageDataString) { 
    return Base64Decode.decode(imageDataString); 
    } 

public IUploader.OnFinishUploaderHandler getOnFinishUploaderHandler() { 
    return onFinishUploaderHandler; 
} 

public void setOnFinishUploaderHandler(IUploader.OnFinishUploaderHandler onFinishUploaderHandler) { 
    this.onFinishUploaderHandler = onFinishUploaderHandler; 
} 

} 

Answer 1

В вашем случае, кажется, что у вас есть только одно изображение в panelImages, поэтому вызов panelImages.clear() должен работать.

Если у вас было больше изображений на панели, и вы хотели удалить последнее изображение, добавленное с помощью загрузчика, вы можете просто сохранить его в переменной класса. Затем вы можете использовать эту переменную для удаления в следующий раз:

private Widget lastImage = null; 

private OnLoadPreloadedImageHandler showImage = new OnLoadPreloadedImageHandler() { 
    public void onLoad(PreloadedImage image) { 
    if (lastImage != null) { 
     lastImage.removeFromParent() 
    } 
    lastImage = image; 
    image.setWidth("75px"); 
    panelImages.add(image); 
    } 
};