傳遞參數後打開新的活動

Question

有人可以幫我嗎？如何通過基本的登錄參數後，打開一個新的活動，這是我的代碼，我不知道發生了什麼事情，我得到一個錯誤：

public class MainActivity extends AppCompatActivity { 

    EditText usern = (EditText)findViewById(R.id.user_name); 
    String user_name = usern.getText().toString(); 
    EditText passw = (EditText)findViewById(R.id.password); 
    String pass_word = passw.getText().toString(); 

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

    /** Called when the user clicks the Send button */ 
    public void nextPage(View view) { 
     // Do something in response to button 
     if (user_name.equals("sheldonmad") && pass_word.equals("password")) { 
      Intent intent = new Intent(this, SecondActivity.class); 
      startActivity(intent); 
     } 
    } 
} 

Answer 1

@Sheldon麥迪遜：嘗試這種方式。需要適當的全局或局部變量的初始化。 請仔細閱讀公文 http://developer.android.com/intl/es/index.html

public class MainActivity extends AppCompatActivity { 

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

     /** Called when the user clicks the Send button */ 
     public void nextPage(View view) { 

     EditText usern = (EditText)findViewById(R.id.user_name); 
     String user_name = usern.getText().toString(); 
     EditText passw = (EditText)findViewById(R.id.password); 
     String pass_word = passw.getText().toString(); 
      // Do something in response to button 
      if (user_name.equals("sheldonmad") && pass_word.equals("password")) { 
       Intent intent = new Intent(this, SecondActivity.class); 
       startActivity(intent); 
      } 
     } 
    } 

Answer 2

嘗試

 public class MainActivity extends AppCompatActivity { 
    EditText usern,passw; 
    String user_name,pass_word; 

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

       usern = (EditText)findViewById(R.id.user_name);      
       passw = (EditText)findViewById(R.id.password);     
       } 

       /** Called when the user clicks the Send button */ 
       public void nextPage(View view) { 

    user_name = usern.getText().toString(); 
    pass_word = passw.getText().toString(); 
        // Do something in response to button 
        if (user_name.equals("sheldonmad") && pass_word.equals("password")) { 
         Intent intent = new Intent(this, SecondActivity.class); 
         startActivity(intent); 
        } 
       } 
      }