问开放活动实例

EN

public class PostActivity extends AppCompatActivity {
    // keep history of viewed posts, with current post at top
    private final Stack<Post> navStack = new Stack<>();

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // get starting link from intent extras and call loadPost(link) 
    }

    private void loadPost(String link){
        // Load post data in background and then call onPostLoaded(post)
        // this is also called when user clicks on a related post link 
    }

    private void onPostLoaded(Post post){
        // add new post to stack
        navStack.push(post);

        // refresh UI
        updateDisplay();
    }

    private void updateDisplay(){

        // take the top Post, without removing it from stack
        final Post post = navStack.peek();

        // Display this post data in UI
    }

    @Override
    public void onBackPressed() {
        // pop the top item
        navStack.pop();

        if(navStack.isEmpty()) {
            // no more items in history, should finish
            super.onBackPressed();
        }else {
            // refresh UI with the item that is now on top of stack
            updateDisplay();
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        // cancel any background post load, release resources
    }
}