How can I set the background color of an Activity to white programatically?
Get a handle to the root layout used, then set the background color on that. The root layout is whatever you called setContentView with.
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(getResources().getColor(android.R.color.red));