在Android中将字符串转换为双精度

问题描述

尝试从 EditText 获取双精度值并在将它们传递给另一个 Intent 之前对其进行操作.不使用原始数据类型，所以我可以使用 toString 方法.

Trying to get double values from an EditText and manipulate them before passing them to another Intent. Not using primitive data type so I can use toString methods.

问题是当我包含 protein=Double.valueOf(p).doubleValue();样式命令，程序强制立即关闭，而不会在 logcat 中留下任何信息.如果我将它们注释掉并设置一些虚拟数据，例如 protein = 1.0;它没有问题.原始数据类型和解析双精度也会发生同样的情况.此代码与普通 java 中的虚拟数据完美配合.我做错了什么?

Problem is when I include the protein=Double.valueOf(p).doubleValue(); style commands, the program force closes immediately without leaving any info in the logcat.If I comment them out and set some dummy data like protein = 1.0; it works with no problems. Same happens with primitive data types and parse double. This code works perfectly with dummy data in normal java. What am I doing wrong?

EditText txtProt, txtCarb, txtFat, txtFiber, txtPoints;
String p, c, f, fi;
Double protein, carbs, fat, fiber;
double temp;
Integer points;

@Override
public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     Log.v("Create Prompt", "ready for layout");
     setContentView(R.layout.main);
     Log.v("Layout Created", "ready for variable assignment");
     txtProt = (EditText) findViewById(R.id.Protein);
     txtCarb = (EditText) findViewById(R.id.Carbs);
     txtFat = (EditText) findViewById(R.id.Fat);
     txtFiber = (EditText) findViewById(R.id.Fiber);
     txtPoints = (EditText) findViewById(R.id.Points);
     btnCalc = (Button) findViewById(R.id.Calc);
     Log.v("Variables Assigned", "ready for double assignment");

     p = txtProt.getText().toString();
     c = txtCarb.getText().toString();
     f = txtFat.getText().toString();
     fi = txtFiber.getText().toString();


     protein=Double.valueOf(p).doubleValue();
     carbs=Double.valueOf(c).doubleValue();
     fat=Double.valueOf(f).doubleValue();
     fiber=Double.valueOf(fi).doubleValue();
     Log.v("Doubles parsed", "ready for calculations");
     //these are the problem statements

     protein = 1.0;
     carbs = 1.0;
     fat = 1.0;
     fiber = 1.0;

     protein *= 16;
     carbs *= 19;
     fat *= 45;
     fiber *= 14;

     temp = protein + carbs + fat - fiber;
     temp = temp/175;

     points = new Integer((int) temp);

推荐答案

我会这样做:

try {
  txtProt = (EditText) findViewById(R.id.Protein); // Same
  p = txtProt.getText().toString(); // Same
  protein = Double.parseDouble(p); // Make use of autoboxing.  It's also easier to read.
} catch (NumberFormatException e) {
  // p did not contain a valid double
}

程序强制立即关闭，而不会在 logcat 中留下任何信息"

"the program force closes immediately without leaving any info in the logcat"

我不知道是否不会在 logcat 输出中留下信息，但强制关闭通常意味着存在未捕获的异常 - 例如 NumberFormatException.

I don't know bout not leaving information in the logcat output, but a force-close generally means there's an uncaught exception - like a NumberFormatException.

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