java.lang.numberformatexception：无效双：“”

Question

收到无效 Double 的错误 java.lang.numberformatexception 无效双精度：“” 这是什么原因

活动 1

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;
    }

       }

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);

     }
    }

我收到 java.lang.numberformatexception invalid double: "" logcat 错误 有人请帮忙

Answer 1

原因是，"" 不是有效的双精度。您需要在之前测试字符串或捕获此类异常

double w;

try {
    w = new Double(input3.getText().toString());
} catch (NumberFormatException e) {
    w = 0; // your default value
}

Answer 2

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，这将始终抛出 @ 987654321@ 解析为double 时因为逗号。

您需要将分隔符从 comma 更改为 point。 您可以通过设置区域设置或使用DecimalFormatSymbols 来更改分隔符。

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;

或者，您可以使用DecimalFormatSymbols 类来更改出现在format 方法生成的格式化数字中的符号。这些符号包括小数分隔符、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);

Answer 3

您应该执行以下操作。把它放在一个 try catch 块中

   double w = new Double(input3.getText().toString());

Answer 4

最好同时测试.equals("") 和null。

假设您在 EditText 上有一个 afterTextChanged 侦听器。当你按下并清除输入的文本时，它会传递!= null，但仍然有""。

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;
    }

Answer 5

基本上，你需要测试你要转成双精度的字符串是否为空。

如果它是empty，那么你可以初始化它用一些值然后继续。

例如：

if(myString.isEmpty()){
myString = ""+0.0;
}
double answer = Double.parseDouble(myString);

Answer 6

 double latitude;
            double longitude;
            try {
                latitude = Double.parseDouble(mApoAppointmentBeanList.get(position).getLatitude());
                longitude = Double.parseDouble(mApoAppointmentBeanList.get(position).getLongitude());

                String uri = String.format(Locale.ENGLISH, "http://maps.google.com/maps?q=loc:%f,%f", latitude, longitude);
                Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(uri));
                startActivity(intent);

            } catch (NumberFormatException e) {
                // your default value
                Toast.makeText(AppointmentsActivity.this, "Invalid location", Toast.LENGTH_LONG).show();
            }