Viewing all current source code problems
(View > Problems or Ctrl+Shift+M
(Cmd+Shift+M on macOS))
Any analysis issues are shown in the Problems pane:

Running and debugging

Note:
  You can debug your app in a couple of ways.

Using DevTools, a suite of debugging and profiling
tools that run in a browser.

Using VS Code’s built-in debugging features,
such as setting breakpoints.

The instructions below describe features available in VS Code.
  For information on using launching DevTools, see
  Running DevTools from VS Code in the DevTools docs.

Start debugging by clicking Run > Start Debugging
from the main IDE window, or press F5.

Selecting a target device

When a Flutter project is open in VS Code,
you should see a set of Flutter specific entries in the status bar,
including a Flutter SDK version and a
device name (or the message No Devices):