按钮在 Android Studio 中只能工作一次

Question

So, i have a button which function is to update my TextView. Every time someone clicks the button to the current date. But, for some reason it only works once. I have tried both XML onClick method and Java setOnClickListener, not one works. Can someone please help me on solving this problem?

import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;

import org.w3c.dom.Text;

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Calendar;
import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extends AppCompatActivity {

    Date date = Calendar.getInstance().getTime();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void btnClick(View i){
        String time = ((EditText) findViewById(R.id.editTextTime)).getText().toString();
        String url = ((EditText) findViewById(R.id.editText)).getText().toString();
        TextView txtErr = findViewById(R.id.errorLog);
        txtErr.setText(date.toString());
    }
}

Answer 1

You are initialising the date only once (when your MainActivity is instantiated). Therefore each time you set the text, you're using the same date instance.

Instead you should be getting a new date each time the button is clicked, something like:

public void btnClick(View i){
        String time = ((EditText) findViewById(R.id.editTextTime)).getText().toString();
        String url = ((EditText) findViewById(R.id.editText)).getText().toString();
        TextView txtErr = findViewById(R.id.errorLog);
        Date date = Calendar.getInstance().getTime();
        txtErr.setText(date.toString());
    }

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As a side note, I wouldn't recommend using the Calendar APIs anymore. Instead take a look at the new, more modern, java.time library which you can take a look at here .