So I'm going along with a lynda.com video on creating a custom list layout. I have gone along with the video but I am not able to change my constructor in order to change the code so it is an array of strings. In both places where I have written MyAdapter, there is a red squiggle below and the top one tells me MyAdapter cannot be resolved to a type. Please assist.
setListAdapter(new MyAdapter<String>(CustomList2Activity.this,
android.R.layout.simple_list_item_1, R.id.textView1, getResources().getStringArray(R.array.companies2)));
private class MyAdapter extends ArrayAdapter<String>{
public MyAdapter(Context context, int resource,
int textViewResourceId, List<String> objects) {
super(context, resource, textViewResourceId, objects);
// TODO Auto-generated constructor stub
}
Make sure you are declaring the MyAdapter class in the right place. Make sure you're not declaring it within a function. Also, go to the source menu (assuming you're using eclipse) and press "organize imports" to make sure your imports are right.
Related
I'm trying to create simple game in C++. At one point I want to have some setting, save and load from config file.
The config file should be read from the beginning, and should be accessible anywhere it needed.
So far I only see Singleton pattern as a solution.
Another way is to create an object an pass it down, but it can mess
up the current code.
I've also search and found something called Dependency Injection.
Is dependency injection useful in C++
Which design patterns can be applied to the configuration settings problem?
But I don't quite understand it, you still have to create an object in main and pass it down, right?
Singleton is quite simple, but some consider it antipattern, while pass it down the tree can mess up my current code. Is there any other Patterns?
P/S: I'm also curious how games load their setting.
I would suggest something simple as the following example, which circumvents any singleton-related or initialization order issue:
struct global_state
{
config _config;
};
struct game_state
{
global_state& _global_state;
};
int main()
{
global_state globals{load_config_from_file()};
game_state game{globals};
game.run();
}
Since _global_state is a member of game_state, it can be used in member functions without the need of explicitly passing it as a parameter:
void game_state::update_ui()
{
const float text_size = _global_state._config.get_float("text_size");
_some_text.set_size(text_size);
}
Developing a Drupal 8 example site, I have declared block in a module, and I want to do a few things with this block, like check the route and show this block only on nodes, also check if the user has permissions to see this block, and the content of the block is a form which I had defined in another place of the module.
I don't want to get the classes/services that I need in a static way, I want to use dependency injection to get those classes because it is technically better to decouple code and allow better testing.
Now "create" method and the "constructor" method on the block are like so:
<?php
public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
return new static(
$configuration,
$plugin_id,
$plugin_definition,
$container->get('current_user'),
$container->get('form_builder'),
$container->get('current_route_match'),
$container->get('access_check.permission')
);
}
public function __construct(
array $configuration, $plugin_id,
$plugin_definition,
AccountProxyInterface $user,
FormBuilderInterface $formBuilder,
ResettableStackedRouteMatchInterface $route,
AccessInterface $access
) {
parent::__construct($configuration, $plugin_id, $plugin_definition);
$this->user = $user;
$this->formBuilder = $formBuilder;
$this->route = $route;
$this->access = $access;
}
Is this the correct way to do this? Maybe I'm doing too much in the block file? Should I create a service to move the logic to another place? Probably I would need more things, which means using more services, and my "create" and "constructor" methods are growing in parameters. Is this the correct way to do it? Thanks.
When you have to inject many services in one class, be it a controller or a block, it usually tells that the class is not well designed because you are (probably) trying lots of things in just one class.
However, I've seen many controllers which inject multiple services in their constructors, so it doesn't seem an unusual practice anyway. "Every rule has an exception".
In the end, I think it is a matter of balance, build a class that is responsible for doing one logical thing, and its dependencies in the same way.
I got the following problem:
I made a custom list CustomList which extends ArrayList and added a new method to it:
public class CustomList extends ArrayList<CustomObj> {
public CustomObj get(String searchName) {
...
}
}
now in my MainActivity.java I make a new object of this CustomList, but I'm using:
List<CustomObj> list = new CustomList(); (1)
and NOT:
CustomList list = new CustomList(); (2)
so far so good!
but when I try to access the function get(String searchName), there is no function I could use!
why? cause when I call it when creating the CustomList via (2) it'll totally work
its is because you are making List(Interface) has no any such method defined , you are making object of CustomList but reference type is List .so it will give you compile time errer if you force to call this method on List reference.This is an example of simple Polymorphism.
You can imagine a case where Mordern car extends Old age car and mordern car has GPS navigation system where as old doesn't in this case if you try to get the detail of navigation system by old car reference which doesn't know about GPS , you wont get anything.
I am working on a system that uses drools to evaluate certain objects. However, these objects can be of classes that are loaded at runtime using jodd. I am able to load a file fine using the following function:
public static void loadClassFile(File file) {
try {
// use Jodd ClassLoaderUtil to load class into the current ClassLoader
ClassLoaderUtil.defineClass(getBytesFromFile(file));
} catch (IOException e) {
exceptionLog(LOG_ERROR, getInstance(), e);
}
}
Now lets say I have created a class called Tire and loaded it using the function above. Is there a way I can use the Tire class in my rule file:
rule "Tire Operational"
when
$t: Tire(pressure == 30)
then
end
Right now if i try to add this rule i get an error saying unable to resolve ObjectType Tire. My assumption would be that I would somehow need to import Tire in the rule, but I'm not really sure how to do that.
Haven't use Drools since version 3, but will try to help anyway. When you load class this way (dynamically, in the run-time, no matter if you use e.g. Class.forName() or Jodd), loaded class name is simply not available to be explicitly used in the code. I believe we can simplify your problem with the following sudo-code, where you first load a class and then try to use its name:
defineClass('Tire.class');
Tire tire = new Tire();
This obviously doesn't work since Tire type is not available at compile time: compiler does not know what type you gonna load during the execution.
What would work is to have Tire implementing some interface (e.g. VehiclePart). So then you could use the following sudo-code:
Class tireClass = defineClass('Tire.class');
VehiclePart tire = tireClass.newInstance();
System.out.println(tire.getPartName()); // prints 'tire' for example
Then maybe you can build your Drools rules over the interface VehiclePart and getPartName() property.
Addendum
Above make sense only when interface covers all the properties of dynamically loaded class. In most cases, this is not a valid solution: dynamically loaded classes simply do not share properties. So, here is another approach.
Instead of using explicit class loading, this problem can be solved by 'extending' the classloader class path. Be warn, this is a hack!
In Jodd, there is method: ClassLoaderUtil.addFileToClassPath() that can add a file or a path to the classloader in the runtime. So here are the steps that worked for me:
1) Put all dynamically created classes into some root folder, with the respect of their packages. For example, lets say we want to use a jodd.samples.TestBean class, that has two properties: number (int) and a value (string). We then need to put it this class into the root/jodd/samples folder.
2) After building all dynamic classes, extend the classloaders path:
ClassLoaderUtil.addFileToClassPath("root", ClassLoader.getSystemClassLoader());
3) load class and create it before creating KnowledgeBuilder:
Class testBeanClass = Class.forName("jodd.samples.TestBean");
Object testBean = testBeanClass.newInstance();
4) At this point you can use BeanUtils (from Jodd, for example:) to manipulate properties of the testBean instance
5) Create Drools stuff and add insert testBean into session:
knowledgeSession.insert(testBean);
6) Use it in rule file:
import jodd.samples.TestBean;
rule "xxx"
when
$t: TestBean(number == 173)
then
System.out.println("!!!");
end
This worked for me. Note that on step #2 you can try using different classloader, but you might need it to pass it to the KnowledgeBuilderFactory via KnowledgeBuilderConfiguration (i.e. PackageBuilderConfiguration).
Another solution
Another solution is to simply copy all object properties to a map, and deal with the map in the rules files. So you can use something like this at step #4:
Map map = new HashMap();
BeanTool.copy(testBean, map);
and later (step #5) add a map to Drools context instead of the bean instance. In this case it would be even better to use defineClass() method to explicitly define each class.
I need to put scriptable NPC in my currect game project.
The project itself is developed in C++ language.
I will using Luabind to bind lua and c++.
I need to call NPC function when certain NPC clicked or timer to do something is activated.
Currently I stuck between 2 NPC script design.
Using a kind of npcname_action to differentiate every NPC.
This is kind of troublesome to give name to every different NPC.
I'm still thinking how to implement this in my project.
Example:
HotelBellboy12_Click() { .. }
HotelBellboy12_TimerAction() { .. }
Using name of function.
Every npc have it own lua file.
I'm thinking to load script into memory and when needed will be loaded into luaState using luaL_loadbuffer
Example:
OnClick() { .. }
OnTimerAction() { .. }
Which one is better and why?
You could use another design.
Take advantage of the fact that table keys and values can be any type.
Let's say npc is a table containing all NPC's. Its keys are NPC' names and its values are another table. This other table keys are the actions, and its values are the function for this actions.
So, if you want bob to jump when clicked on, and alice to cry after a timer, simply do :
npc.bob.click = function () jump() end
npc.alice.timer = function () cry() end
I've done something like this before and I used something similar to your #2 option. When the map loads I load a configuration Lua file containing all the NPC data; among that is the name of the script file used for the NPC.
When I need to load the NPC in the game I compile the Lua file. NPC's can use a 'model' NPC type to dictate most of the common behavior (for example a Merchant type or a Commoner type) which is specified in the NPC configuration. These model types provide all the basic functionality such as providing a trade window when clicked. The specific NPC's use functions like OnClick() to override their model and provide custom handlers.
This worked pretty well for me, although it ends up being a large volume of scripts if your game gets large.