如何從另一個活動禁用按鈕

Question

我有這個小登錄程序將數據保存到共享首選項。主要活動有「登錄」和「帳戶」按鈕。我想要禁用登錄按鈕時，共享首選項爲空，並啓用用戶的「帳戶」按鈕註冊一個帳戶，這是我的第二活動。如果共享首選項爲空，如何啓用/禁用2個按鈕？

1. 活動1個

   protected void onCreate(Bundle savedInstanceState) { 
   super.onCreate(savedInstanceState); 
   setContentView(R.layout.main_interface); 
   
   final Button login = (Button)findViewById(R.id.Login); 
   final Button account = (Button)findViewById(R.id.Account); 
   login.setEnabled(false); 
   login.setOnClickListener(new OnClickListener() { 
       public void onClick(View arg0) { 
        startActivity(new Intent(MainActivity.this, Summation.class)); 
   
       } 
   }); 
   
   
   account.setOnClickListener(new OnClickListener() { 
       public void onClick(View arg0) { 
        startActivity(new Intent(MainActivity.this, Append.class)); 
       } 
   }); 
   Button exit = (Button)findViewById(R.id.Exit); 
   exit.setOnClickListener(new OnClickListener() { 
       public void onClick(View arg0) { 
        finish(); 
        System.exit(0); 
       } 
   }); 
   

2. 活動2

   protected void onCreate(Bundle savedInstanceState){ 
   super.onCreate(savedInstanceState); 
   Stetho.initializeWithDefaults(this); 
   setContentView(R.layout.append_interface); 
   
   
   final EditText usernameAppend = (EditText)findViewById(R.id.usernameAppend); 
   final EditText passwordAppend = (EditText)findViewById(R.id.passwordAppend); 
   
   //this buttons appends the username and password to the SharedPreferences 
   Button append = (Button)findViewById(R.id.Append); 
   append.setOnClickListener(new View.OnClickListener() { 
       public void onClick(View arg0) { 
        final SharedPreferences mySharedPref = getSharedPreferences(PREF_NAME, MODE_PRIVATE); 
        final SharedPreferences.Editor editor = mySharedPref.edit(); 
        //Append get data 
        final String un = usernameAppend.getText().toString(); 
        editor.putString(editorUsername,un); 
        editor.commit(); 
        final String pw = passwordAppend.getText().toString(); 
        editor.putString(editorPassword, pw); 
        editor.commit(); 
        if(mySharedPref != null){ 
         Toast.makeText(Append.this,"Account saved",Toast.LENGTH_LONG).show(); 
   
         startActivity(new Intent(Append.this, MainActivity.class)); 
   
        }else{ 
         Toast.makeText(Append.this,"Please enter again",Toast.LENGTH_LONG).show(); 
   
        } 
   
        } 
   
       } 
   ); 
   //Exit button,, exits the app 
   Button exit = (Button)findViewById(R.id.Exit); 
   exit.setOnClickListener(new View.OnClickListener() { 
   public void onClick(View arg0) { 
       finish(); 
       System.exit(0); 
       } 
   }); 
   
   } 
   

Answer 1

在第一活動檢查任一共享的偏好存在與否。第一次它將是空的。

 btnLogin.setEnabled(false); 
    btnAccount.setEnabled(false); 
    SharedPreferences mPrefs=this.getSharedPreferences(Your_Preference_Name,Context.MODE_PRIVATE); 
    if(mPrefs==null) 
    { 
     btnAccount.setEnabled(true); 
    } 
    btnAccount.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 

     } 
    }); 
    btnLogin.setOnClickListener(new View.OnClickListener() { 
     @Override 
     public void onClick(View view) { 

     } 
    });