帶有用戶輸入的AlertDialog在單擊確定按鈕時顯示NullPointerException

Question

如果在SharedPreferences中可用，我的Activity應顯示用戶的名稱和郵件地址。如果沒有Dialog被啓動，其向用戶請求信息。

的Dialog彈出，但點擊OK按鈕活動時拋出一個NullPointerException與以下日誌，這是指向else聲明：

10-29 10:36:59.745: E/AndroidRuntime(16518): FATAL EXCEPTION: main 
10-29 10:36:59.745: E/AndroidRuntime(16518): java.lang.NullPointerException 
10-29 10:36:59.745: E/AndroidRuntime(16518): at de.blubb.blubb.Blubb$1.onClick(Blubb.java:79) 
10-29 10:36:59.745: E/AndroidRuntime(16518): at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166) 
10-29 10:36:59.745: E/AndroidRuntime(16518): at android.os.Handler.dispatchMessage(Handler.java:99) 
10-29 10:36:59.745: E/AndroidRuntime(16518): at android.os.Looper.loop(Looper.java:137) 
10-29 10:36:59.745: E/AndroidRuntime(16518): at android.app.ActivityThread.main(ActivityThread.java:4759) 
10-29 10:36:59.745: E/AndroidRuntime(16518): at java.lang.reflect.Method.invokeNative(Native Method) 
10-29 10:36:59.745: E/AndroidRuntime(16518): at java.lang.reflect.Method.invoke(Method.java:511) 
10-29 10:36:59.745: E/AndroidRuntime(16518): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 
10-29 10:36:59.745: E/AndroidRuntime(16518): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:558) 
10-29 10:36:59.745: E/AndroidRuntime(16518): at dalvik.system.NativeStart.main(Native Method)  

我的代碼：

public class Blubb extends Activity { 
public static final String username = "nameKey"; // for Shared Preferences 
public static final String mailaddress = "mailKey"; // for Shared Preferences 
public static final String BlubbPrefs = "preferences" ; 
private static final int DIALOG_ALERT = 10; // constant for identifying the preference dialog 

@Override 
    protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    //addPreferencesFromResource(R.xml.preferences); 
    setContentView(R.layout.activity_blubb); 

    TextView viewUserName = (TextView) findViewById(R.id.viewUserNamen); 
    TextView viewUserMail = (TextView) findViewById(R.id.viewMailAdresse); 

    SharedPreferences settings = getSharedPreferences(BlubbPrefs, Context.MODE_PRIVATE); 

    String name = settings.getString(username, ""); 
    String mail = settings.getString(mailaddress, ""); 

    /* Test if user settings are available */ 
    if ("".equals(name) || !"".equals(mail)) { 
     System.out.println("Nutzerangaben fehlen"); 
/* Requesting user settings with a Dialog */   
     showDialog(DIALOG_ALERT); 
     } 
    if (settings.contains(username)){ 
     viewUserName.setText(settings.getString(username, "")); 
     } 
    if (settings.contains(mailaddress)){ 
     viewUserMail.setText(settings.getString(mailaddress, "")); 
     } 
} 

public Dialog onCreateDialog(int id) { 
    switch (id) { 
    case DIALOG_ALERT: 
    /* Create the new Dialog. */ 
     Context context = Blubb.this; 
     AlertDialog.Builder builder = new AlertDialog.Builder(context); 
     //Builder builder = new AlertDialog.Builder(this); 
     LayoutInflater inflater = (LayoutInflater) this.getSystemService(LAYOUT_INFLATER_SERVICE); 
     builder.setView(inflater.inflate(R.layout.dialog_settings, null)); 
     builder.setCancelable(false); 

    /* OK-Button */  
     builder.setPositiveButton(R.string.button_send, new DialogInterface.OnClickListener() { 
      public void onClick(DialogInterface dialog, int arg1) {     
       final EditText editName = (EditText)findViewById(R.id.editUserNamen); 
       final EditText editMail = (EditText)findViewById(R.id.editMailAdresse); 

       /* Prove user settings */ 
       if (editName.getText().toString().trim().length() <= 0){ 
        editName.setError("Name missing"); 
        Toast.makeText(getApplicationContext(), "Name missing", Toast.LENGTH_LONG).show(); 
        //showAlertNameMissing(); 
        } 
       /*if (!inputMailAdresse.contains(".") || !inputMailAdresse.contains("@")) { */ 
       if (editMail.getText().toString().trim().contains(".") || editMail.getText().toString().trim().contains("@")){ 
        editMail.setError("Mail incorrect"); 
        Toast.makeText(getApplicationContext(), "Mail incorrect", Toast.LENGTH_LONG).show(); 
        //showAlertMailMissing(); 
        } 
       else {      
        final String inputUserNamen = editName.getText().toString().trim(); 
        final String inputMailAdresse = editMail.getText().toString().trim(); 
        /* Reading access on preferences.xml */ 
        SharedPreferences settings = getSharedPreferences(BlubbPrefs, Context.MODE_PRIVATE); // MODE_PRIVATE => can only be accessed by this application 
        /* Object of type editor to get writing access on preferences.xml */ 
        SharedPreferences.Editor editor = settings.edit(); 
        /* Saving key/value pairs to preferences.xml */ 
        editor.putString(username, inputUserNamen); 
        editor.putString(mailaddress, inputMailAdresse); 
        /* Writing key/value pairs to preferences.xml */ 
        editor.commit(); 

        Toast.makeText(getApplicationContext(), R.string.alert_saved, Toast.LENGTH_SHORT).show(); 
        //return; 
        }     
       dialog.dismiss(); 
       } 
      } 
     ); 
    /* Cancel-Button */   
     builder.setNegativeButton(R.string.button_cancel, new DialogInterface.OnClickListener() { 
      public void onClick(DialogInterface dialog, int arg1) { 
       dialog.dismiss(); 
       Toast.makeText(getApplicationContext(), "Input cancelled", Toast.LENGTH_LONG).show(); 
       } 
      });   

     AlertDialog dialog = builder.create(); 
     dialog.show(); 
    } 
    return super.onCreateDialog(id); 
} 
}  

作爲編程的新手，當然還有Java，我一直試圖通過搜索互聯網和改變我的代碼來找到2周的解決方案。但是現在我很困惑。

解決了這個問題後我還會遇到Dialog關閉問題here？有誰能夠幫助我？

Answer 1

空指針在編輯文本中最具有可能性。在你的代碼之前，你將相同的ID轉換爲textViews，現在你將它們轉換爲EditTexts，相同的佈局不能爲兩種不同類型的視圖使用相同的ID。

TextView viewUserName = (TextView) findViewById(R.id.editUserNamen); //on your activity 
EditText editName = (EditText)findViewById(R.id.editUserNamen); //on your dialog 

這是最可能的錯誤。