Question

我现在只需要一点帮助。该应用程序运行良好，但当你输入前。美元，2到SEK它的结果是13,38。但如果我将金额改为3则没有任何反应。我必须来回改变电流才能做出改变。我希望应用程序在更改值后立即更改结果。请帮忙！:)

package com.example.currencyconverter;

import android.app.Activity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;


public class MainActivity extends Activity {
 private String [] currency_name;
 private ArrayAdapter<String> adapter;
 private Spinner spin1, spin2;

 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);



 setUpTheSpinners();



 }
 @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        return true;
    }


 private void setUpTheSpinners() {
 currency_name = getResources().getStringArray(R.array.currency_name);
 adapter= new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, currency_name);
 adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
 OnItemSelectedListener listener = new CurrencySelectedListener();
 spin1 = (Spinner)findViewById(R.id.spinner1);
 spin1.setAdapter(adapter);
 spin1.setOnItemSelectedListener(listener);
 spin2 = (Spinner)findViewById(R.id.spinner2);
 spin2.setAdapter(adapter);
 spin2.setOnItemSelectedListener(listener);
 }


 private void calculateSum() {
 String [] rates = getResources().getStringArray(R.array.currency_rate);
 int index1 = spin1.getSelectedItemPosition();
 int index2 = spin2.getSelectedItemPosition();
 double rate1 = Double.parseDouble( rates[index1] );
 double rate2 = Double.parseDouble( rates[index2] );

 EditText editAmount = (EditText) findViewById(R.id.editText1);
if (!TextUtils.isEmpty(editAmount.getText().toString())) {
    double amount = Double.valueOf(editAmount.getText().toString());

    double totalRate = amount * rate1 / rate2;
     TextView totalRateText = (TextView)findViewById(R.id.editText2);
     totalRateText.setText("" + totalRate);

    }




 }

 private class CurrencySelectedListener implements OnItemSelectedListener {

 public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
 calculateSum();
 }

 public void onNothingSelected(AdapterView<?> parent) {
 }
 }
}

Answer 1

您的editAmount.getText().toString()值为NULL（空）。而且您仍尝试将此值转换为DOUBLE，以便获得NumberFormatException。

在解析之前检查editText值：

if(!editAmount.getText().toString().equals(""))
{
//Do your job
}

或者另一种方式是

if (!TextUtils.isEmpty(editAmount.getText().toString())) {
//Do your job
}

货币应用需要更新

1 个答案: