Android：试图转换时货币转换器崩溃

Question

这里的第一次程序员。所以我使用Eclipse创建了一个权重转换器，在这里我输入一个值并使用2个spinners来选择单位并在下一个活动中显示结果。每当它尝试转换输入值时，我的转换器崩溃。我没有问题显示我的输入值到我的下一个活动，但每当我启用转换逻辑它崩溃时，我按转换按钮。

我的主要活动做的转换和传递给其他意图

package com.example.currencyconverter2; 

import android.app.Activity; 
import android.content.Intent; 
import android.os.Bundle; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.widget.ArrayAdapter; 
import android.widget.EditText; 
import android.widget.Spinner; 

public class MainActivity extends Activity { 
Spinner fromCurrency; 
Spinner toCurrency; 
public static String final1; 
double result; 

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

@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; 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle action bar item clicks here. The action bar will 
    // automatically handle clicks on the Home/Up button, so long 
    // as you specify a parent activity in AndroidManifest.xml. 
    int id = item.getItemId(); 
    if (id == R.id.action_settings) { 
     return true; 
    } 
    return super.onOptionsItemSelected(item); 
} 


/*protected void onResume{ 
    super.onResume(); 
    setUpSpinnerData(); 
}*/ 
//Sets the data for the Spinner to display 
public void setSpinnerData(){ 
    fromCurrency = (Spinner)findViewById(R.id.from_currency); 
    toCurrency = (Spinner)findViewById(R.id.to_currency); 
    ArrayAdapter <String> from = new ArrayAdapter<String>(this,R.array.currencySpinnerChoices,android.R.layout.simple_list_item_1); 
    ArrayAdapter <String> to = new ArrayAdapter<String>(this,R.array.currencySpinnerChoices,android.R.layout.simple_list_item_1); 
    fromCurrency.setAdapter(from); 
    toCurrency.setAdapter(to); 
    } 

//New intent on button press with inserted data 
public void showResult(View v){ 

    Intent i = new Intent(this, MainResultActivity.class); 
    EditText editconvert = (EditText) findViewById(R.id.amount); 
    String string1 = editconvert.getText().toString(); 
    //double value = Double.parseDouble(string1); 

    int cho1 = fromCurrency.getSelectedItemPosition(); 
    int cho2 = toCurrency.getSelectedItemPosition(); 
    double value = Double.parseDouble(editconvert.getText().toString()); 

    double ratio[] = {1.0f, 0.001f, 1.0e-6f, 1.0e-9f}; 
    double result = value/ratio[cho1] * ratio[cho2]; 

    i.putExtra(final1, result); 
    startActivity(i);  
    } 
} 

我的onCreate方法我在其他活动显示结果

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main_result); 

    //MainActivity.class.getIntent(); 
    Intent intent = getIntent(); 

    double value = intent.getDoubleExtra(MainActivity.final1,0);   
    TextView tv = (TextView)findViewById(R.id.result_value); 

    tv.setText(value+" ");  
} 

我logcat的

12-02 05:50:40.002: E/AndroidRuntime(1528): FATAL EXCEPTION: main 
12-02 05:50:40.002: E/AndroidRuntime(1528): Process: com.example.currencyconverter2, PID: 1528 
12-02 05:50:40.002: E/AndroidRuntime(1528): java.lang.IllegalStateException: Could not execute method of the activity 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at android.view.View$1.onClick(View.java:3823) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at android.view.View.performClick(View.java:4438) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at android.view.View$PerformClick.run(View.java:18422) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at android.os.Handler.handleCallback(Handler.java:733) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at android.os.Handler.dispatchMessage(Handler.java:95) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at android.os.Looper.loop(Looper.java:136) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at android.app.ActivityThread.main(ActivityThread.java:5017) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at java.lang.reflect.Method.invokeNative(Native Method) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at java.lang.reflect.Method.invoke(Method.java:515) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at dalvik.system.NativeStart.main(Native Method) 
12-02 05:50:40.002: E/AndroidRuntime(1528): Caused by: java.lang.reflect.InvocationTargetException 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at java.lang.reflect.Method.invokeNative(Native Method) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at java.lang.reflect.Method.invoke(Method.java:515) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at android.view.View$1.onClick(View.java:3818) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  ... 11 more 
12-02 05:50:40.002: E/AndroidRuntime(1528): Caused by: java.lang.NullPointerException 
12-02 05:50:40.002: E/AndroidRuntime(1528):  at com.example.currencyconverter2.MainActivity.showResult(MainActivity.java:68) 
12-02 05:50:40.002: E/AndroidRuntime(1528):  ... 14 more 

相当新，所以我不明白logcat错误，谁能解释一下？

Answer 1

初始化您的final1字符串。

public static String final1="result"; 

，并使用setSpinnerData()方法

Answer 2

toCurrency和fromCurrency从不intialized初始化toCurrency和fromCurrency因为你执行setSpinnerData这两个领域，它不被任何所谓的初始化。

Answer 3

> public static String final1; 

这从来没有在您的代码中设置。