关于学习Android Java：学习Android Java – 应用程序失败

Learning Android Java - application fails

我一直在努力学习Java for Android开发，所以我决定尝试制作一个简单的转换器应用程序来学习。目前我有一个简单的用户界面，我正在尝试从摄氏温度转换为华氏温度。转换器在工作时会转换为Celsius，Fahrenheit和Kelvin。

当我单击应该运行计算方法的按钮时，我收到错误"不幸的是，转换器已停止"。
下面是我的代码，我也为视图包含了XML。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94

package com.michaelmurphy.converter;

import android.app.Activity;
import android.os.Bundle;
import android.widget.EditText;
import android.widget.Spinner;

public class Temperature extends Activity {

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{

super.onCreate(savedInstanceState);
setContentView(R.layout.temperature_view);

// TODO Auto-generated method stub
}

public void tempCalc()
{
//define variables
float value = 0;
String from ="";//for spinner
String to ="";//for spinner

//get entered value
EditText input = (EditText) findViewById(R.id.editText1);
//convert to string
String enteredValue = input.getText().toString();
//convert string into float
float num = Float.valueOf(enteredValue);

//retrieve the from spinner value
final Spinner fromSpinner = (Spinner) findViewById(R.id.spinner1);
from = fromSpinner.getSelectedItem().toString();
//retrieve the to spinner value
final Spinner toSpinner = (Spinner) findViewById(R.id.spinner1);
to = toSpinner.getSelectedItem().toString();

EditText output = (EditText) findViewById(R.id.textView2);

/*if(from.equals(to)) //the same conversion type
{
//error
}*/

if(from.equals("Celcius"))
{
if(to.equals("Fahrenheit"))
{
value = celToFar(num);
}
else
{
//value = celToKel(num);
}
}
else if(from.equals("Fahrenheit"))
{
if(to.equals("Celcius"))
{
//value = fahToCel(num);
}
else
{
//value = fahToKel(num);
}
}
else //kelvin
{
if(to.equals("Celcius"))
{
//value = kelToCel(num);
}
else
{
//value = kelToFah(num);
}
}

//set the label to variable value
String valueStr = Float.toString(value);//cast float to string
output.setText(valueStr);
}

public float celToFar(float cel)
{
float fah = cel * 9/5 + 32;
return fah;
}

}

查看XML代码：

有人能够指出我哪里出错了，我不知道。谢谢