import java.io.*;
import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;
public class Exercise17_09 extends Application {
// Specify the size of five string fields in the record
final static int NAME_SIZE = 32;
final static int STREET_SIZE = 32;
final static int CITY_SIZE = 20;
final static int STATE_SIZE = 2;
final static int ZIP_SIZE = 5;
final static int RECORD_SIZE =
(NAME_SIZE + STREET_SIZE + CITY_SIZE + STATE_SIZE + ZIP_SIZE);
// Access address.dat using RandomAccessFile
private RandomAccessFile raf;
// Text fields
private TextField tfName = new TextField();
private TextField tfStreet = new TextField();
private TextField tfCity = new TextField();
private TextField tfState = new TextField();
private TextField tfZip = new TextField();
// Buttons
private Button btAdd = new Button("Add");
private Button btFirst = new Button("First");
private Button btNext = new Button("Next");
private Button btPrevious = new Button("Previous");
private Button btLast = new Button("Last");
private Button btUpdate = new Button("Update");
public Exercise17_09() {
// Open or create a random access file
try {
raf = new RandomAccessFile("address.dat", "rw");
}
catch(IOException ex) {
ex.printStackTrace();
System.exit(1);
}
}
@Override
public void start(Stage primaryStage) {
tfState.setPrefColumnCount(2);
tfZip.setPrefColumnCount(4);
tfCity.setPrefColumnCount(12);
// Pane p1 for holding labels java基础篇17章 Name, Street, and City
GridPane p1 = new GridPane();
p1.setAlignment(Pos.CENTER);
p1.setHgap(5);
p1.setVgap(5);
p1.add(new Label("Name"), 0, 0);
p1.add(new Label("Street"), 0, 1);
p1.add(new Label("City"), 0, 2);
p1.add(tfName, 1, 0);
p1.add(tfStreet, 1, 1);
HBox p2 = new HBox(5);
p2.getChildren().addAll(tfCity, new Label("State"), tfState,
new Label("Zip"), tfZip);
p1.add(p2, 1, 2);
// Add buttons to a pane
HBox p3 = new HBox(5);
p3.getChildren().addAll(btAdd, btFirst, btNext, btPrevious,
btLast, btUpdate);
p3.setAlignment(Pos.CENTER);
// Add p1 and p3 to a border pane
BorderPane borderPane = new BorderPane();
borderPane.setCenter(p1);
borderPane.setBottom(p3);
// Create a scene and place it in the stage
Scene scene = new Scene(borderPane, 400, 120);
primaryStage.setTitle("Exercise17_09"); // Set the stage title
primaryStage.setScene(scene); // Place the scene in the stage
primaryStage.show(); // Display the stage
// Display the first record if exists
try {
if (raf.length() > 0) readAddress(0);
}
catch (IOException ex) {
ex.printStackTrace();
}
btAdd.setOnAction(e -> {
try {
writeAddress(raf.length());
}
catch (Exception ex) {
}
});
btFirst.setOnAction(e -> {
try {
if (raf.length() > 0) readAddress(0);
}
catch (IOException ex) {
}
});
btNext.setOnAction(e -> {
try {
long currentPosition = raf.getFilePointer();
if (currentPosition < raf.length())
readAddress(currentPosition);
}
catch (IOException ex) {
}
});
btPrevious.setOnAction(e -> {
try {
long currentPosition = raf.getFilePointer();
if (currentPosition - 2 * RECORD_SIZE > 0)
// Why 2 * 2 * RECORD_SIZE? See the follow-up remarks
readAddress(currentPosition - 2 * 2 * RECORD_SIZE);
else
readAddress(0);
}
catch (IOException ex) {
}
});
btLast.setOnAction(e -> {
try {
long lastPosition = raf.length();
if (lastPosition > 0)
// Why 2 * RECORD_SIZE? See the follow-up remarks
readAddress(lastPosition - 2 * RECORD_SIZE);
}
catch (IOException ex) {
}
});
btUpdate.setOnAction(e -> {
try {
writeAddress(raf.getFilePointer() - 2 * RECORD_SIZE);
}
catch (IOException ex) {
}
});
}
/ Write a record at the end of the file */
public void writeAddress(long position) {
try {
raf.seek(position);
FixedLengthStringIO.writeFixedLengthString(
tfName.getText(), NAME_SIZE, raf);
FixedLengthStringIO.writeFixedLengthString(
tfStreet.getText(), STREET_SIZE, raf);
FixedLengthStringIO.writeFixedLengthString(
tfCity.getText(), CITY_SIZE, raf);
FixedLengthStringIO.writeFixedLengthString(
tfState.getText(), STATE_SIZE, raf);
FixedLengthStringIO.writeFixedLengthString(
tfZip.getText(), ZIP_SIZE, raf);
}
catch (IOException ex) {
ex.printStackTrace();
}
}
/ Read a record at the specified position */
public void readAddress(long position) throws IOException {
raf.seek(position);
String name = FixedLengthStringIO.readFixedLengthString(
NAME_SIZE, raf);
String street = FixedLengthStringIO.readFixedLengthString(
STREET_SIZE, raf);
String city = FixedLengthStringIO.readFixedLengthString(
CITY_SIZE, raf);
String state = FixedLengthStringIO.readFixedLengthString(
STATE_SIZE, raf);
String zip = FixedLengthStringIO.readFixedLengthString(
ZIP_SIZE, raf);
tfName.setText(name);
tfStreet.setText(street);
tfCity.setText(city);
tfState.setText(state);
tfZip.setText(zip);
}
/
* The main method is only needed for the IDE with limited
* JavaFX support. Not needed for running from the command line.
*/
public static void main(String[] args) {
launch(args);
}
}
class FixedLengthStringIO {
/ Read fixed number of characters from a DataInput stream */
public static String readFixedLengthString(int size,
DataInput in) throws IOException {
// Declare an array of characters
char[] chars = new char[size];
// Read fixed number of characters to the array
for (int i = 0; i < size; i++)
chars[i] = in.readChar();
return new String(chars);
}
/ Write fixed number of characters to a DataOutput stream */
public static void writeFixedLengthString(String s, int size,
DataOutput out) throws IOException {
char[] chars = new char[size];
// Fill in string with characters
s.getChars(0, s.length(), chars, 0);
// Fill in blank characters in the rest of the array
for (int i = Math.min(s.length(), size); i < chars.length; i++)
chars[i] = ' ';
// Create and write a new string padded with blank characters
out.writeChars(new String(chars));
}
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