无法解析

Question

我是人，我有一个很大的问题：我正在用Db创建我的第一个Android应用程序，这是我第二周使用java和OOP。

这是主要活动的来源：

public class EpsoftSMSActivity extends Activity { 
    /** Called when the activity is first created. */ 



    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

     final MyDatabase db=new MyDatabase(getApplicationContext()); 



     db.open(); //apriamo il db 



     if (db.listaParametri().getCount()==0) 
     { 

      setup_parametri(); 

      /*final Dialog dialog = new Dialog(this); 
      dialog.setContentView(R.layout.login); 
      dialog.setTitle("Login"); 
      dialog.setCancelable(true); 
      //there are a lot of settings, for dialog, check them all out! 




      //set up button 
      Button registra = (Button) dialog.findViewById(R.id.registra); 
      registra.setOnClickListener(new OnClickListener() { 
       @Override 
        public void onClick(View v) { 

         String username = dialog.findViewById(R.id.username).toString(); 
         String password = dialog.findViewById(R.id.password).toString(); 

         db.inserimentoParametri(username, password); 
         dialog.dismiss(); 
        } 
      }); 

      Button annulla = (Button) dialog.findViewById(R.id.annulla); 

      annulla.setOnClickListener(new OnClickListener() { 
       @Override 
        public void onClick(View v) { 
         dialog.dismiss(); 

        } 
      }); 

      //now that the dialog is set up, it's time to show it  
      dialog.show();*/ 

     } 




    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) 
    { 
     getMenuInflater().inflate(R.layout.menu, menu); 
     return true; 
    } 


    public boolean onOptionsItemSelected(MenuItem item) 
    { 
     switch (item.getItemId()) 
     { 
      case R.id.chiudi: 

       finish(); 
       System.exit(0); 
       return true; 

      case R.id.setup: 

       setup_parametri(); 



       return true; 

      case R.id.info: 

        final Dialog dialog = new Dialog(this); 
        dialog.setContentView(R.layout.dialog); 
        dialog.setTitle("Informazioni & Credits"); 
        dialog.setCancelable(true); 
        //there are a lot of settings, for dialog, check them all out! 

        /* //set up text 
        TextView text = (TextView) dialog.findViewById(R.id.TextView01); 
        //text.setText(R.string.lots_of_text); 

        //set up image view 
        ImageView img = (ImageView) dialog.findViewById(R.id.ImageView01); 
        img.setImageResource(R.drawable.ic_launcher);*/ 

        //set up button 
        //set up button 
        Button button = (Button) dialog.findViewById(R.id.Button01); 
        button.setOnClickListener(new OnClickListener() { 
        @Override 
         public void onClick(View v) { 
          dialog.dismiss(); 

         } 
        }); 
        //now that the dialog is set up, it's time to show it  
        dialog.show(); 


      return true; 

     } 
     return super.onOptionsItemSelected(item); 
    } 

    public void setup_parametri() 
    { 



     final Dialog dialog = new Dialog(this); 
     dialog.setContentView(R.layout.login); 
     dialog.setTitle("Login"); 
     dialog.setCancelable(true); 
     //there are a lot of settings, for dialog, check them all out! 




     //set up button 
     Button registra = (Button) dialog.findViewById(R.id.registra); 
     registra.setOnClickListener(new OnClickListener() { 
      @Override 
       public void onClick(View v) { 

        String username = dialog.findViewById(R.id.username).toString(); 
        String password = dialog.findViewById(R.id.password).toString(); 

         db.inserimentoParametri(username, password); 
        dialog.dismiss(); 
       } 
     }); 

     Button annulla = (Button) dialog.findViewById(R.id.annulla); 

     annulla.setOnClickListener(new OnClickListener() { 
      @Override 
       public void onClick(View v) { 
        dialog.dismiss(); 

       } 
     }); 

     //now that the dialog is set up, it's time to show it  
     dialog.show(); 


    } 


} 

在最新的功能，被称为“setup_parametri”我尝试叫“db.inserimentoParametri”，但是Eclipse告诉我，“分贝不能得到解决”。 Db在oncreate中定义。

Whatsup？ TNX。

Answer 1

您已经声明DB作为内onCreate()的变量，而不将它传递给setup_parametri()

您需要可以使其成为类变量：

public class EpsoftSMSActivity extends Activity { 
    /** Called when the activity is first created. */ 


    final MyDatabase db; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

     db = new MyDatabase(getApplicationContext()); 



     db.open(); //apriamo il db 

或setup_parametri()签名更改为setup_parametri(MyDatabase db)

Answer 2

db是在onCreate()内部声明的局部变量。它对任何其他方法都是不可见的。您可能希望将其设置为Activity类的实例字段，这意味着它将适用于该类的所有方法。

声明onCreate()以外的字段，但在里面进行初始化。像这样：

private MyDatabase db; 

@Override 
public void onCreate(Bundle savedInstanceState) { 

    .... 

    db = new MyDatabase(getApplicationContext()); 

Answer 3

当您的OnClickerListener事件处理程序运行时，DB变量不在作用域中。

将db定义移动到onCreate方法的范围之外，即使其成为成员变量。