Question

我试图将lambda函数转换为java并且我没有成功。我拥有的C＃代码是

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace DelegateEventsWindowsFormsApp
{
    public partial class Form1 : Form
    {
        public delegate void RecordUpdated(int iRecordId, EventArgs e);
        public event RecordUpdated recordUpdated;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.recordUpdated += (iRecord, Arg) =>
            {
                MessageBox.Show(iRecord.ToString());
            };
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (recordUpdated != null)
                recordUpdated(100, null);
        }
    }
}

我怎么能把它转换成java？预期的行为是表单1有一个按钮，当我点击按钮时，如果recordUpdated已订阅，那么我显示100.如果它为null，则recordUpdated更新为100。

我已经完成了以下java代码，

由于存在异步调用，我做了一些事情，

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends Activity {

    private String EventrecordUpdated;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        this.EventrecordUpdated = null;

        EventServiceClass obj = new EventServiceClass();

        Toast.makeText(getApplicationContext(), "Calling Service",
                Toast.LENGTH_LONG).show();

        obj.testService("TEST");

        Toast.makeText(getApplicationContext(), "DOne Service",
                Toast.LENGTH_LONG).show();
        setContentView(R.layout.activity_main); // here we initialize the
                                                // component. ( our UI)

    }

    public void delegateRecordUpdated(String iRecordId, String e) {

        Toast.makeText(getApplicationContext(), iRecordId, Toast.LENGTH_LONG)
                .show();

    }

    public void EventrecordUpdate(String iRecordId, String e) {

        this.EventrecordUpdated = iRecordId;
        Toast.makeText(getApplicationContext(), "Subscribed to the Event",
                Toast.LENGTH_LONG).show();

    }

    public void button1_Click(View view) { // this is the
        setContentView(R.layout.activity_main);

        new LongOperation().execute("123");

        /*
         * if (EventrecordUpdated != null) { delegateRecordUpdated("100", null);
         * } else { EventrecordUpdate("100", null); }
         */

    }

    private class LongOperation extends AsyncTask<String, Void, String> {

        @Override
        protected String doInBackground(String... params) {

            System.out.println(params);

            return "Executed";
        }

        @Override
        protected void onPostExecute(String result) {

            Toast.makeText(getApplicationContext(), "Executed",
                    Toast.LENGTH_LONG).show();
        }

        @Override
        protected void onPreExecute() {
        }

        @Override
        protected void onProgressUpdate(Void... values) {
        }
    }

}

Answer 1

在Java中执行此操作的方法如下（使用包含的帮助程序类＆＃39; EventSimulation＆＃39;） - 请注意，您需要在Java中选择自己的首选项，以便＆＃39; Form＆＃39;以及相应的Form_Load和button1_Click，但这将显示与C＃事件等效的通用Java：

package DelegateEventsWindowsFormsApp;

public class Form1 extends Form //you need your own 'Form' equivalent
{
    @FunctionalInterface
    public interface RecordUpdated
    {
        void invoke(int iRecordId);
    }
    public EventSimulation<RecordUpdated> recordUpdated = new EventSimulation<RecordUpdated>();

    private void Form1_Load()
    {
        this.recordUpdated.addListener((iRecord) ->
        {
            //substitute your own Java preference for the message box:
            //javax.swing.JOptionPane.showConfirmDialog(null, iRecord.toString());
        });
    }

    private void button1_Click()
    {
        if (recordUpdated != null)
        {
            for (RecordUpdated listener : recordUpdated.anonymousListeners)
            {
                listener.invoke(100);
            }

            //uncomment the following if you also subscribe to the event using method names:
            //for (RecordUpdated listener : recordUpdated.namedListeners.values())
            //{
            //  listener.invoke(100);
            //}
        }
    }
}

public final class EventSimulation<T>
{
    public java.util.List<T> anonymousListeners = new java.util.ArrayList<T>();
    public void addListener(T unnamedEventHandlerMethod)
    {
        anonymousListeners.add(unnamedEventHandlerMethod);
    }

    //you don't need the following for your example, but this would be required for the  
    //Java equivalent to the more common C# event subscribing/unsubscribing via method names:
    public java.util.Map<String, T> namedListeners = new java.util.HashMap<String, T>();
    public void addListener(String methodName, T namedEventHandlerMethod)
    {
        if (!namedListeners.containsKey(methodName))
            namedListeners.put(methodName, namedEventHandlerMethod);
    }
    public void removeListener(String methodName)
    {
        if (namedListeners.containsKey(methodName))
            namedListeners.remove(methodName);
    }
}

将C＃中的lambda函数转换为java

1 个答案: