Android Studio 中参数的圆形浮点数或双精度数

Question

我已经阅读了很多关于如何对数字进行舍入的文章，无论是浮点数还是双精度数以显示，例如，只有两位小数，当你使用已经定义的变量时它看起来很容易，但在我的情况下，所有数字都是通过 InputEditText 输入的，我不知道应该把小数限制放在哪里，所以，例如，显示“2543.789906”，它显示“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 + "");
    }
}

感谢您的帮助。

Answer 1

试试这个方法

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

Android Studio 中参数的圆形浮点数或双精度数

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