官术网_书友最值得收藏!

Time for action – using an InlineDateField component

Let's change the DateField example a little bit:

  1. Open or import the datefield example in your IDE.
  2. Replace DateField with InlineDateField in DateFieldUI.java.
  3. Deploy and run the example.

What just happened?

This is the result you get:

You cannot type the year now, you have to select it from the component.

Uploading files

Study this simple example that displays (in the console) the content of a text file uploaded by the user:

public class UploadUI extends UI implements Receiver {
  @Override
  protected void init(VaadinRequest request) {
 Upload upload = new Upload(
 "Select a text file and look at the console",
 this);

    VerticalLayout layout = new VerticalLayout();
    layout.addComponent(upload);
    setContent(layout);
  }

  @Override
  public OutputStream receiveUpload(String filename,
      String mimeType) {
 return new OutputStream() {
 @Override
 public void write(int b) throws IOException {
 System.out.print((char) b);
 }
 };
  }


}

The Upload class displays a native (browser-dependent) button to select a file and a Vaadin button to upload the file to the server:

We are passing a Receiver interface (implemented in our UploadUI class) to process the upload byte-by-byte. The receiveUpload method must return an OutputStream class that writes the content of the file being uploaded. In this example, we are taking each byte and printing it on the console, but you can do with the bytes whatever you want to. For example, you could write them to a file in the hard disk or in a BLOB in an SQL database.

No, really, how can we actually write the file to the server? OK, OK, here is a possible implementation of recieveUpload that does the job:

@Override
public OutputStream receiveUpload(String filename,
    String mimeType) {
  FileOutputStream output = null;

  try {
    output = new FileOutputStream("C:\\Users\\Alejandro\\"
        + filename);
  } catch (FileNotFoundException e) {
    e.printStackTrace();
  }
  return output;
}

Pop quiz – thinking in Vaadin

Check your knowledge:

Q1. Which method allows you to add options in a ComboBox?

  1. addOption(String option).
  2. addItem(String itemId).
  3. addItem(Object itemId).

Q2. If you want to execute some code when the user changes the value in a Field component you must add a:

  1. ValueChangeListener.
  2. ClickListener.
  3. ValueChangeEvent.

Q3. To add a tooltip, you use the method:

  1. setTooltip(String text).
  2. addTooltip(String text).
  3. setDescription(String text).

Q4. You can add an error message to a Component by calling:

  1. setErrorMessage(String error).
  2. setComponentError(ErrorMessage errorMessage).

Q5. All input components implement (directly or indirectly):

  1. Field.
  2. Property.
  3. All of the above.

Q6. A Property is:

  1. A value of a certain type.
  2. A collection of items.
主站蜘蛛池模板: 大关县| 东明县| 青神县| 湖北省| 渝北区| 筠连县| 广安市| 汶川县| 于都县| 屏南县| 阿合奇县| 乌兰察布市| 宁南县| 全州县| 无棣县| 梅河口市| 泰宁县| 兰溪市| 土默特右旗| 南京市| 辽阳县| 青冈县| 革吉县| 柞水县| 永泰县| 石河子市| 鹤峰县| 襄城县| 德保县| 中西区| 锡林郭勒盟| 德保县| 外汇| 肥城市| 庄河市| 宝兴县| 锦屏县| 麻城市| 高雄市| 嘉鱼县| 常宁市|