class 내에서 layout background 수정

setContentView(R.layout.main);

  // Now get a handle to any View contained 
  // within the main layout you are using
  View someView = findViewById(R.id.randomViewInMainLayout);

  // Find the root view
  View root = someView.getRootView()

  // Set the color
  root.setBackgroundColor(android.R.color.red);







출처 ; http://stackoverflow.com/questions/4761686/how-to-set-background-color-of-activity-to-white-programmatically