# Java/Kotlin (Android Studio)
## Using Java
### Download .jar library
Download the NEP Java library using the next link:
[Download nep-0.0.1.jar](https://bitbucket.org/enriquecoronadozu/nep-installers/downloads/nep-0.0.1.jar)
{% hint style="info" %}
This tutorial needs NEP-CLI to version 0.2.0 or above, or NEP+ App 0.0.5 or above.
{% endhint %}
### Include .jar library
1. **Copy .jar to the "libs" Directory:** Navigate to the **apps/libs** directory in the Android Studio project and copy and paste the .jar file, such as the figure below.
2. **Include the required `.jar` file in Your Project:** In Android Studio open build.gradle(Module:app) located in Grandle Scripts -> build.gradle and the next **dependencies**:
{% code title="bundle.gradle(:app)" %}
```json
implementation 'org.zeromq:jeromq:0.5.2'
implementation 'com.google.code.gson:gson:2.10.1'
implementation files('/libs/nep-0.0.1.jar')
```
{% endcode %}
3. **Sync Gradle Files:** Click on the "Sync Project with Gradle Files" button in the toolbar. This action ensures that the newly added library is properly included in your project's build configuration.
4. **Verify the Gradle Sync:** Once the Gradle sync is complete, verify that there are no errors in the Gradle console.
5. **Configure Network Permissions:** Since your app will be using network sockets, you need to ensure that your AndroidManifest.xml file includes the necessary permissions. Add the following permission to your manifest file:
{% code title="Android.Manifest.xml" %}
```xml
```
{% endcode %}
### Create a simple publisher:
Import NEP libraries to the MainActivity file as follows:
{% code title="MainActivity.java" %}
```java
import nep.Node;
import nep.Publisher;
```
{% endcode %}
Modify the MainActivity class as follows:
public class MainActivity extends AppCompatActivity {
private Publisher pub;
private Node node;
private String nepMasterIP = "192.168.0.178";
private int index = 0;
private static class JsonValue {
int result;
public JsonValue(int result) {
this.result = result;
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
node = new Node("android_test");
pub = node.new_pub("test", "json", nepMasterIP);
}
public void onClickBtn(View v)
{
if (pub.started)
{
JsonValue jsonValue = new JsonValue(index++);
pub.publish(jsonValue);
}
}
Update `nepMasterIP` (line 6) with the IP address of the computer running the NEP master server (using NEP-CLI or NEP+ App).
Add a button in activity\_main.xml and inside the XML layout (code ) file set its `onClick` attribute to execute a function named `onClickBtn`
In this example `onClick` attribute is set in line 5.
### Add a simple subscriber:
For this example, we need to import the next packages/libraries:
```java
import nep.Subscriber;
import com.google.gson.Gson;
import android.os.AsyncTask;
import java.io.IOException;
```
To the previous code, we will add a background thread or AsyncTask to perform socket communication operations. AsyncTask is a convenient way to perform background tasks and update the UI thread with the results.
Here's an example of how you can define an AsyncTask to handle socket communication:
```java
public class SubscriberTask extends AsyncTask {
private Node node;
private Subscriber sub;
// Constructor to initialize the node
public SubscriberTask(Node node) {
this.node = node;
}
@Override
protected Void doInBackground(Void... params) {
// Perform socket communication operations here
// This method runs on a background thread
// Create a new subscriber with the topic <'test'>
sub = node.new_sub("test", "json", nepMasterIP);
while (!isCancelled()) {
String msg = null; // Message obtained as an String
try {
msg = sub.listen();
} catch (IOException e) {
throw new RuntimeException(e);
}
if (!"{}".equals(msg)) // If message is not {}
{
System.out.println(msg);
// Then, convert string to Java object
Gson gson = new Gson();
JsonValue obj = gson.fromJson(msg,JsonValue.class);
// Print message
System.out.println(obj.result);
}
}
// Clean up resources when finished
sub.close();
return null;
}
@Override
protected void onProgressUpdate(String... values) {
// Update the UI with the received message
String message = values[0];
// Handle the received message as needed
}
}
```
After defining the AsyncTask, you can create an instance of it and execute it to start listening to the subscriber. You can execute the AsyncTask in the `onCreate()` method of your Activity or wherever appropriate.
Ensure that you properly handle cleanup when your AsyncTask is no longer needed. You can cancel the AsyncTask and clean up resources in the `onDestroy()` method of your Activity or wherever appropriate.
```java
@Override
protected void onDestroy() {
super.onDestroy();
if (subscriberTask != null) {
subscriberTask.cancel(true);
}
}
```
An example of putting it all together is shown below:
...
import nep.Node;
import nep.Publisher;
import nep.Subscriber;
import com.google.gson.Gson;
import android.os.AsyncTask;
import java.io.IOException;
public class MainActivity extends AppCompatActivity {
private Publisher pub;
private Node node;
private String nepMasterIP = "192.168.0.178";
private int index = 0;
SubscriberTask subscriberTask;
private static class JsonValue {
int result;
public JsonValue(int result) {
this.result = result;
}
}
public class SubscriberTask extends AsyncTask<Void, String, Void> {
private Node node;
private Subscriber sub;
// Constructor to initialize the node
public SubscriberTask(Node node) {
this.node = node;
}
@Override
protected Void doInBackground(Void... params) {
// Perform socket communication operations here
// This method runs on a background thread
// Create a new publisher with the topic <'test'>
sub = node.new_sub("test", "json", nepMasterIP);
while (!isCancelled()) {
String msg = null; // Message obtained as an String
try {
msg = sub.listen();
} catch (IOException e) {
throw new RuntimeException(e);
}
if (!"{}".equals(msg)) // If message is not {}
{
System.out.println(msg);
// Then, convert string to Java object
Gson gson = new Gson();
JsonValue obj = gson.fromJson(msg,JsonValue.class);
// Print message
System.out.println(obj.result);
}
}
// Clean up resources when finished
sub.close();
return null;
}
@Override
protected void onProgressUpdate(String... values) {
// Update the UI with the received message
String message = values[0];
// Handle the received message as needed
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
node = new Node("android_test");
pub = node.new_pub("test", "json", nepMasterIP);
subscriberTask = new SubscriberTask(node);
subscriberTask.execute();
}
public void onClickBtn(View v)
{
if (pub.started)
{
JsonValue jsonValue = new JsonValue(index++);
pub.publish(jsonValue);
}
}
@Override
protected void onDestroy() {
super.onDestroy();
if (subscriberTask != null) {
subscriberTask.cancel(true);
}
}
}
