【Android】在非Activity下使用startActivity()

會出現以下提示

Calling startActivity() from outside of an Activity  context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?

解決辦法很簡單
加上FLAG_ACTIVITY_NEW_TASK flag就可以。

Intent starter = new Intent(context, MainActivity.class);
starter.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
//starter.putExtra("from", from);

context.startActivity(starter);