java.lang.numberformatexception：无效双：“”
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java.lang.numberformatexception: invalid double: " "
提问by no0bCoder
getting an error of invalid Double java.lang.numberformatexception invalid double: "" what is the reason for this
得到一个 invalid Double 的错误 java.lang.numberformatexception invalid double: "" 这是什么原因
Activity 1
活动一
package com.example.solarcalculator;
import android.os.Bundle;
import android.widget.Button;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.EditText;
import android.app.AlertDialog;
import android.content.Intent;
@SuppressLint("UseValueOf")
public class MainActivity extends Activity {
private EditText input1;
private EditText input2;
private EditText input3;
private EditText input4;
private EditText input5;
private MainActivity mContext;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mContext = this;
setContentView(R.layout.activity_main);
input5 = (EditText) findViewById(R.id.input5);
Button button1 = (Button) findViewById(R.id.button1);
input4 = (EditText) findViewById(R.id.input4);
input1 = (EditText) findViewById(R.id.input1);
input2 = (EditText) findViewById(R.id.input2);
input3 = (EditText) findViewById(R.id.input3);
button1.setOnClickListener(new OnClickListener() {
@SuppressWarnings("unused")
private AlertDialog show;
@SuppressLint("UseValueOf")
@Override
public void onClick(View arg0) {
if ( (input4.getText().toString() == " ")
|| (input4.getText().length() ==0) ||
(input5.getText().length() == 0)
|| (input5.getText().toString() == " ")){
show = new AlertDialog.Builder(mContext).setTitle("Error")
.setMessage("Some inputs are empty")
.setPositiveButton("OK", null).show();
}
else if ((input1.getText().length() != 0) &&
(input3.getText().length() ==0) && (input2.getText().length() == 0)){
double w = new Double(input3.getText().toString());
double t = new Double(input4.getText().toString());
double x = new Double(input5.getText().toString());
float e = 7;
double num = 1000*x;
double den = w*t*e;
double payback = num/den;
double money = w*t*e/1000;
Intent intent = new Intent(MainActivity.this, Power.class);
intent.putExtra("payback", payback);
intent.putExtra("money", money);
startActivity(intent);
}
else if ((input1.getText().length() == 0) && (input3.getText().length() != 0) &&
(input2.getText().length() != 0)){
double t = new
Double(input4.getText().toString());
double x = new Double(input5.getText().toString());
double v = new Double(input2.getText().toString());
double i = new Double(input3.getText().toString());
float e = 7;
double num = 1000*x;
double den = v*i*t*e;
double payback = num/den;
double money = v*i*t*e/1000;
Intent intent = new Intent(MainActivity.this, Power.class);
intent.putExtra("payback", payback);
intent.putExtra("money", money);
startActivity(intent);
}
else {
double t = new Double(input4.getText().toString());
double x = new Double(input5.getText().toString());
double v = new Double(input2.getText().toString());
double i = new Double(input3.getText().toString());
float e = 7;
double num = 1000*x;
double den = v*i*t*e;
double payback = num/den;
double money = v*i*t*e/1000;
Intent intent = new Intent(MainActivity.this, Power.class);
intent.putExtra("payback", payback);
intent.putExtra("money", money);
startActivity(intent);
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
Activity2
活动2
package com.example.solarcalculator;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
@SuppressLint("NewApi")
public class Power extends Activity {
private double money;
private double payback;
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.power);
payback = getIntent().getDoubleExtra("payback",0);
money = getIntent().getDoubleExtra("money", 0);
TextView pay = (TextView) findViewById(R.id.textView2);
String payback1 = Double.toString(payback);
pay.setText(payback1);
TextView mon = (TextView) findViewById(R.id.textView4);
String money1 = Double.toString(money);
mon.setText(money1);
}
}
I am getting java.lang.numberformatexception invalid double: "" error in logcat anyone please help
我收到 java.lang.numberformatexception invalid double: "" error in logcat 任何人请帮忙
采纳答案by flx
The reason is, that "" is not a valid double. You need to test the String before or catch such exceptions
原因是，“”不是有效的双倍。您需要先测试 String 或捕获此类异常
double w;
try {
w = new Double(input3.getText().toString());
} catch (NumberFormatException e) {
w = 0; // your default value
}
回答by Raghunandan
You should do as below. Put it inside a try catch block
你应该做如下。把它放在一个 try catch 块中
double w = new Double(input3.getText().toString());
回答by Aditya Naique
Better to also test for .equals("")along with null.
最好也.equals("")与null.
Consider you have an afterTextChanged listener on an EditText. When you back press and clear the entered text, it'll pass != null, but still have "".
假设您在 EditText 上有一个 afterTextChanged 侦听器。当你回按并清除输入的文本时，它会通过!= null，但仍然有"".
This worked for me:
这对我有用：
double myDouble;
String myString = ((EditText) findViewById(R.id.editText1)).getText().toString();
if (myString != null && !myString.equals("")) {
myDouble = Double.valueOf(myString);
} else {
myDouble = 0;
}
回答by Forntoh
The value of the double depends on the language of the device.For example, for devices in french the number 0.179927becomes 0,179927which will always throw a NumberFormatExceptionwhen parsing it to doublebecause of the comma.
double 的值取决于设备的语言。例如，对于法语设备，数字0.179927变为0,179927，由于逗号，NumberFormatException在解析它时总是会抛出 a double。
You need to change the separator from a commato a point.
You can change the separator either by setting a locale or using the DecimalFormatSymbols.
您需要将分隔符从 a 更改comma为 a point。您可以通过设置区域设置或使用DecimalFormatSymbols.
If you want the grouping separator to be a point, you can use a european locale:
如果您希望分组分隔符是一个点，您可以使用欧洲语言环境：
NumberFormat nf = NumberFormat.getNumberInstance(Locale.GERMAN);
DecimalFormat df = (DecimalFormat)nf;
Alternatively you can use the DecimalFormatSymbolsclass to change the symbols that appear in the formatted numbers produced by the formatmethod. These symbols include the decimal separator, the grouping separator, the minus sign, and the percent sign, among others:
或者，您可以使用DecimalFormatSymbols该类来更改出现在该format方法生成的格式化数字中的符号。这些符号包括小数点分隔符、分组分隔符、减号和百分号等：
DecimalFormatSymbols otherSymbols = new DecimalFormatSymbols(currentLocale);
otherSymbols.setDecimalSeparator(',');
otherSymbols.setGroupingSeparator('.');
DecimalFormat df = new DecimalFormat(formatString, otherSymbols);
回答by Akshay Chopra
Basically, you need to testwhether the stringthat you want to convert into double is empty or not.
基本上，您需要测试要转换为 double的字符串是否为空。
If it is empty, then you can just initialise itwith some value and then proceed further.
如果它是空的，那么你可以用一些值初始化它，然后继续进行。
For example:
例如：
if(myString.isEmpty()){
myString = ""+0.0;
}
double answer = Double.parseDouble(myString);
