从参数在 Android Studio 中舍入浮点数或双数

Question

I've been reading a lot of posts about how to round numbers, either float or double to show, for example, only two decimals, it looks easy when you do it using already defined variables, but in my case, all numbers are entered through InputEditText, and I don't know where I should put the decimal limitation, so that instead of, for example, showing "2543.789906" it shows "2534.78"

**My code:**

package com.example.converfuel;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;

import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

public class Timeextends MainActivity {

    private Spinner spinner1, spinner2;
    private Button btnSubmit;
    private EditText from;
    private TextView to;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_masa);

        btnSubmit = (Button) findViewById(R.id.btnSubmit);
        from = (EditText) findViewById(R.id.InputEditText);
        to = (TextView) findViewById(R.id.OutputTextView);

        spinner1 = (Spinner) findViewById(R.id.spinner1);
        List<String> list1 = new ArrayList<String>();
        list1.add("Nanosecond");
        list1.add("Microsecond");
        list1.add("Milisecond");
        list1.add("Second");
        list1.add("Minute");
        list1.add("Hour");
        list1.add("Day");
        list1.add("Week");
        list1.add("Month");
        list1.add("Year");
        list1.add("Decade");
        list1.add("Century");
        ArrayAdapter<String> dataAdapter1 = new ArrayAdapter<String>(this,
                android.R.layout.simple_spinner_item, list1);
        dataAdapter1.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner1.setAdapter(dataAdapter1);


        spinner2 = (Spinner) findViewById(R.id.spinner2);
        List<String> list2 = new ArrayList<String>();
        list2.add("Nanosecond");
        list2.add("Microsecond");
        list2.add("Milisecond");
        list2.add("Second");
        list2.add("Minute");
        list2.add("Hour");
        list2.add("Day");
        list2.add("Week");
        list2.add("Month");
        list2.add("Year");
        list2.add("Decade");
        list2.add("Century");
        ArrayAdapter<String> dataAdapter2 = new ArrayAdapter<String>(this,
                android.R.layout.simple_spinner_item, list2);
        dataAdapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner2.setAdapter(dataAdapter2);
    }


    public void onClick (View v){

        int index1 = spinner1.getSelectedItemPosition();
        int index2 = spinner2.getSelectedItemPosition();
        float value = Float.parseFloat(from.getText().toString());

//
//

        float ratio[] = {3.154e+18f, 3.154e+15f, 3.154e+12f, 3.154e+9f, 5.256e+7f, 876000f, 36500f, 5214f, 1200f, 100f, 10f, 1.0f};
        float result = value / ratio[index1] * ratio[index2];
        to.setText(result + "");
    }
}

Thanks for your help.

Answer 1

Try this way

 DecimalFormat df = new DecimalFormat("#.##");
 String strResult = String.valueOf(Double.valueOf(df.format(result)));
 to.setText(strResult);