Question

当我运行我的程序时，当我进行下面的部门时，我的响应总是为0？我已经阅读了一篇关于堆栈的文章，但它似乎更复杂，涉及多个变量，我无法看到它是一样的。如果有人能在我的if和else语句中提供有关数学错误的任何帮助，我将非常感激。对不起，我是新的，这是我的第一语言：/。

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;

import java.text.DecimalFormat;


public class MainActivity extends ActionBarActivity {

    int inchesPerFoot = 12;
    int feetPerYard = 3;
    int yardsPerMile = 1760;
    double unitsRequested;
    double totalUnits;
    String unitChoice;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final EditText units = (EditText)findViewById(R.id.txtNumberOfUnits);
        final Spinner Conversion = (Spinner)findViewById(R.id.Units_Array);
        Button Submit = (Button)findViewById(R.id.btn_Submit);
        Submit.setOnClickListener(new View.OnClickListener() {
        final TextView result = ((TextView)findViewById(R.id.txt_Result));
            @Override
            public void onClick(View v) {
                unitsRequested = Integer.parseInt(units.getText().toString());
                DecimalFormat number = new DecimalFormat("###,###.##");
                if (Conversion.equals(inchesPerFoot))
                        totalUnits = (inchesPerFoot / unitsRequested);
                else
                if (Conversion.equals(feetPerYard))
                        totalUnits = (feetPerYard / unitsRequested);
                else
                if (Conversion.equals(yardsPerMile))
                        totalUnits = (yardsPerMile / unitsRequested);
                unitChoice = Conversion.getSelectedItem().toString();
                result.setText("Total Units for " + unitChoice +" is "+ number.format(totalUnits));
            }
        });

    }

Answer 1

您正在将Spinner对象与某些int值进行比较，例如：

if (Conversion.equals(inchesPerFoot))

这是一个毫无意义的比较，永远不会是真的，所以你的计算totalUnits没有达到任何条件，所以答案是零。

Conversion的类型为Spinner，inchesPerFoot为int。您需要获取微调器位置索引并与之进行比较，如下所示：

int spinnerIndex = Conversion.getSelectedItemPosition();
if (spinnerIndex == 0)
    totalUnits = (inchesPerFoot / unitsRequested);
else
if (spinnerIndex == 1)
    totalUnits = (feetPerYard / unitsRequested);
else
if (spinnerIndex == 2)
    totalUnits = (yardsPerMile / unitsRequested);

（假设您的微调器项目按此顺序），或者获取所选的微调器项目内容（假设它是包含整数的字符串）并使用：

int spinnerValue = Integer.parseInt(Conversion.getSelectedItem().toString());

或者，您可以将微调器项内容作为String获取，并针对不同的转换类型进行String比较：

String spinnerValue = Conversion.getSelectedItem().toString();

Answer 2

你在这里是我过去使用它的最终解决方案。

公共类MainActivity扩展了ActionBarActivity {

final double inchesPerFoot = 12;
final double feetPerYard = 3;
final double yardsPerMile = 1760;
double unitsRequested;
double totalUnits;
String unitChoice;



@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    final EditText units = (EditText)findViewById(R.id.txtNumberOfUnits);
    final Spinner Conversion = (Spinner)findViewById(R.id.Units_Array);
    Button Submit = (Button)findViewById(R.id.btn_Submit);
    Submit.setOnClickListener(new View.OnClickListener() {
    final TextView result = ((TextView)findViewById(R.id.txt_Result));
        @Override
        public void onClick(View v) {
            unitsRequested = Integer.parseInt(units.getText().toString());
            DecimalFormat number = new DecimalFormat("###,###.##");
            unitChoice = Conversion.getSelectedItem().toString();

            if (unitChoice.equals("Inches to Feet"))
                totalUnits = (unitsRequested / inchesPerFoot);
            else
            if (unitChoice.equals("Feet to Yards"))
                    totalUnits = (unitsRequested / feetPerYard);
            else
            if (unitChoice.equals("Yards to Miles"))
                    totalUnits = (unitsRequested / yardsPerMile);

            result.setText("Total Units for " + unitChoice +" is "+ number.format(totalUnits));
        }
    });

}

Android：Division总是0

2 个答案: