拋出一個按鈕的空指針異常

Question

因此，我檢查了R.id.button（我的按鈕ID的名稱）以確保它很好，但是任何時候我嘗試運行單擊按鈕時，它都會嚇壞了Log Cat告訴我我有一個空指針異常。任何幫助，將不勝感激，代碼如下。

public class RSSReaderActivity extends Activity { 
     RSSParser RSStext; 
     public EditText url; 
     Button feedButton; 
     /** Called when the activity is first created. */ 
     @Override 
     public void onCreate(Bundle savedInstanceState) { 

      super.onCreate(savedInstanceState); 
      url = (EditText) findViewById(R.id.url_text); 
      feedButton = (Button) findViewById(R.id.button); 
      setContentView(R.layout.main); 
     } 

     public boolean onCreateOptionsMenu (Menu menu){ 
      MenuInflater inflater = getMenuInflater(); 
      inflater.inflate(R.menu.menu, menu); 
      return true;//true makes visible 
     } 

     public boolean onOptionsItemSelected(MenuItem item){ 
      switch(item.getItemId()){ 
       case R.id.exit: this.finish(); 
      } 
      return true;//true makes visible 
     } 

     public void parser(View view){//test code 
      if(url.equals(null)){ //This is the line where my error is thrown according to log cat 
       Toast toast = Toast.makeText(getApplicationContext(), "No URL entered!", 5); 
       toast.show(); 
      } 
      else{ 
       String temp = url.toString(); 
       RSStext = new RSSParser(temp); 
      } 
     } 
    } 

和XML我的主類：

<?xml version="1.0" encoding="utf-8"?> 
    <LinearLayout android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:gravity="center|top" 
     android:orientation="vertical" xmlns:android="http://schemas.android.com/apk/res/android"> 

     <TextView 
      android:layout_width="wrap_content" 
      android:layout_height="0dp" 
      android:layout_weight="1" 
      android:text="@string/hello" /> 

     <EditText 
      android:id="@+id/url_text" 
      android:layout_width="fill_parent" 
      android:layout_height="0dp" 
      android:layout_weight="1" 
      android:clickable="true" 
      android:inputType="textUri" 
      android:text="@string/default_url" /> 

     <Button 
      android:id="@+id/button" 
      android:layout_width="wrap_content" 
      android:layout_height="0dp" 
      android:layout_weight="1" 
      android:onClick="parser" 
      android:text="@string/feed_button" /> 

    </LinearLayout> 

Answer 1

你獲得的EditText

@Override 
    public void onCreate(Bundle savedInstanceState) { 

     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 
     url = (EditText) findViewById(R.id.url_text); 
     feedButton = (Button) findViewById(R.id.button); 

    }