Android工作室：應用程序崩潰 -

Question

這是在用戶點擊時更改背景色的java代碼。在設備上運行時，它顯示「不幸的應用程序已停止工作」。

public class MainActivity extends AppCompatActivity { 
    RelativeLayout myLayout=(RelativeLayout)findViewById(R.id.layout1); 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 

    myLayout.setBackgroundColor(Color.YELLOW); 
    Button redbtn=(Button)findViewById(R.id.btn1); 
    Button bluebtn=(Button)findViewById(R.id.btn2); 
    redbtn.setOnClickListener(
      new View.OnClickListener() { 
       @Override 
       public void onClick(View v) { 
        myLayout.setBackgroundColor(Color.RED); 
       } 
      } 
    ); 
    bluebtn.setOnClickListener(
      new View.OnClickListener() { 
       @Override 
       public void onClick(View v) { 
        myLayout.setBackgroundColor(Color.BLUE); 
       } 
      } 
    ); 
    myLayout.addView(redbtn); myLayout.addView(bluebtn); 
    //setContentView(myLayout); 
} 

Answer 1

public class MainActivity extends AppCompatActivity { 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    RelativeLayout myLayout=(RelativeLayout)findViewById(R.id.layout1); 
    myLayout.setBackgroundColor(Color.YELLOW); 
    Button redbtn=(Button)findViewById(R.id.btn1); 
    Button bluebtn=(Button)findViewById(R.id.btn2); 
    redbtn.setOnClickListener(
      new View.OnClickListener() { 
       @Override 
       public void onClick(View v) { 
        myLayout.setBackgroundColor(Color.RED); 
       } 
      } 
    ); 
    bluebtn.setOnClickListener(
      new View.OnClickListener() { 
       @Override 
       public void onClick(View v) { 
        myLayout.setBackgroundColor(Color.BLUE); 
       } 
      } 
    ); 
    myLayout.addView(redbtn); myLayout.addView(bluebtn); 
    //setContentView(myLayout); 
}