title: How to make layout's and view's background transparent?
body: <p>I'm trying to make a layout with a background and add a scroll view at the bottom of this layout.</p>
  
  <p>here's my code:</p>
  
  <pre><code>FrameLayout mainLayout = new FrameLayout(getApplicationContext());
  mainLayout.setLayoutParams(new ViewGroup.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
  mainLayout.setBackgroundResource(R.drawable.background2);
  
  
  FrameLayout.LayoutParams params = new FrameLayout.LayoutParams(LayoutParams.FILL_PARENT, 200);
  params.gravity = Gravity.BOTTOM|Gravity.CENTER;
  
  
  final ScrollView scrollView = new ScrollView(getApplicationContext());
  scrollView.setLayoutParams(params);
  scrollView.setBackgroundColor(Color.TRANSPARENT);
  
  StorageView storageView = new StorageView(getApplicationContext());
  storageView.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
  
  Drawable drawable = getResources().getDrawable(R.drawable.background1);
  drawable.setAlpha(0);
  storageView.setBackgroundDrawable(drawable);
  
  scrollView.addView(storageView);
  
  mainLayout.addView(scrollView);
  
  setContentView(mainLayout);
  </code></pre>
  
  <p>why I see only the background image?</p>
  
  <p>*Edit:</p>
  
  <p>If I remove all the setBackgroundColor and move the setBackgroundDrawable to the ScrollLayout or the StorageView I see the background on the whole screen</p>
  
  <p>*Edit2:</p>
  
  <p>I edit the code: I remove the unnecessary layouts, and set a background drawable with alpha set to 0, and now it works.</p>
  
  <p>well, I'll be happy if someone explain to me why I need to do this? </p>