title: Call a method in another Activity on launch, and redirect user to that Activity
body: <p>I have built an app with two Activities.</p>
  
  <p>Activity two is a grid template, which a user can add content to, and provide with a title. (See image below on right).</p>
  
  <p>Activity one, is my apps landing page (see image below, on left) - this contains a link to multiple grids that the user has created. Each Grid is represented on the landing page by a square containing the Grids title.</p>
  
  <p>A user can click the button on the bottom right of the Landing Page and this will launch a new blank grid (this takes up the full screen). They can add content to the grid. Then click a button on the bottom right of the grid to save it. This redirects them back to the landing page, and a thumbnail containing the grid title is added to the landing page. Clicking a thumbnail that already exists on the landing page, will open the corresponding saved grid with the content that was previously added. </p>
  
  <p>The thumbnails on the landing page have been created as Fragments. The 'Grid' is just an Activity - it does not use any Fragments - everything is contained in the Activity, and it initiates a custom GridAdapter class.</p>
  
  <p>I have built the two independently. I am now trying to build the logic to:</p>
  
  <p>Add a Fragment containing the Grid Title to the Landing Page, whenever a Grid is saved.</p>
  
  <p>The only way I can see of doing this, is to:</p>
  
  <ol>
  <li>Create a method in the Landing Page Activity that adds a fragment to the grid.</li>
  <li>Set onClickListener for the 'Save Grid' button in the Grid Activity. This calls the method in the Landing Page Activity that adds a fragment, and passes in the Grid title, and then redirects the user back to the Landing Page. </li>
  <li>Or, the 'SaveGrid' button redirects the user back to the landing page, and the landing page activity detects that it is being 'resumed' after the user has clicked the 'SaveGrid' button, and so calls the 'addfragment' method. (I don't yet know if this is possible).</li>
  </ol>
  
  <p>I am new to android programming, and have just read that it is bad practice to call a method from one activity to another. I am also concerned about creating multiple activities for the Grid (I thought these were like classes, which acts as a blueprint, and you instantiate multiples of them, and I also thought Activity was the only option, as they take up the full screen). </p>
  
  <p>I guess, there are therefore 2 questions:</p>
  
  <p>1) Is my logic OK to use an Activity for the Grid, knowing that there will be multiples of these created.</p>
  
  <p>2) Is it OK to call a method in one Activity from another Activity in order to add a new Fragment to the Landing Page whenever a new Grid is added.</p>
  
  <p>Can anyone advise on the best way to approach this to ensure I am complying with best practice?</p>
  
  <p><a href="https://i.stack.imgur.com/dhBff.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dhBff.jpg" alt="Landing Page"></a> <a href="https://i.stack.imgur.com/RBTN4.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RBTN4.jpg" alt="Grid Page"></a></p>