Question

这里的第一次程序员。所以我正在使用Eclipse创建一个权重转换器，我输入一个值并使用2个微调器来选择单位并在下一个活动中显示结果。每当尝试转换输入值时，我的转换器就会崩溃。我没有问题将我的输入值显示在我的下一个活动上，但是当我启用转换逻辑时，当我按下转换按钮时它会崩溃。

我的主要活动进行转换并传递给其他意图

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);       
  }  
}

我的其他活动中的onCreate方法显示结果

  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+" ");      
}

我的LogCat

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，所以我不理解logcat错误，任何人都可以解释一下吗？

Answer 1

初始化了您的final1字符串。

public static String final1="result";

以及使用toCurrency方法

初始化fromCurrency和setSpinnerData()

Answer 2

toCurrency和fromCurrency从未初始化，因为您在setSpinnerData中执行了这两个字段的初始化，而这些字段在任何地方都没有被调用。

Answer 3

>  public static String final1;

这从未在您的代码中设置。

Android：货币转换器在尝试转换时崩溃

3 个答案: