<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">

<EditText
    android:id="@+id/editText_username"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="32dp"
    android:layout_marginStart="32dp"
    android:layout_marginTop="128dp"
    android:ems="10"
    android:inputType="textPersonName"
    android:text=""
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />


<TextView
    android:id="@+id/textView_username"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="8dp"
    android:layout_marginLeft="32dp"
    android:layout_marginStart="32dp"
    android:text="Фамилия имя: "
    app:layout_constraintBottom_toTopOf="@+id/editText_username"
    app:layout_constraintStart_toStartOf="parent" />

<EditText
    android:id="@+id/editText_email"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="32dp"
    android:layout_marginStart="32dp"
    android:layout_marginTop="32dp"
    android:ems="10"
    android:inputType="textEmailAddress"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/editText_username" />

<TextView
    android:id="@+id/textView_email"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="8dp"
    android:layout_marginLeft="32dp"
    android:layout_marginStart="32dp"
    android:text="E-Mail:"
    app:layout_constraintBottom_toTopOf="@+id/editText_email"
    app:layout_constraintStart_toStartOf="parent" />

<EditText
    android:id="@+id/editText_password"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginEnd="32dp"
    android:layout_marginStart="32dp"
    android:layout_marginTop="32dp"
    android:ems="10"
    android:inputType="textPassword"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.0"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/editText_email" />


<TextView
    android:id="@+id/textView_password"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="8dp"
    android:layout_marginLeft="32dp"
    android:layout_marginStart="32dp"
    android:text="Пароль:"
    app:layout_constraintBottom_toTopOf="@+id/editText_password"
    app:layout_constraintStart_toStartOf="parent" />

<Button
    android:id="@+id/button"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:layout_marginBottom="32dp"
    android:layout_marginEnd="32dp"
    android:layout_marginStart="32dp"
    android:text="Зарегестрироваться"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent" />


</android.support.constraint.ConstraintLayout>

public class RegistrationActivity extends AppCompatActivity{

private UserRegistrationTask userRegistrationTask;


@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_registration);
    final EditText editTextUsername = findViewById(R.id.editText_username);
    final EditText editTextEmail = findViewById(R.id.editText_email);
    final EditText editTextPassword = findViewById(R.id.editText_password);
    Button registration = findViewById(R.id.button_registration);

    registration.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String username = String.valueOf(editTextUsername.getText());
            String email = String.valueOf(editTextEmail.getText());
            String password = String.valueOf(editTextPassword.getText());

            userRegistrationTask = new UserRegistrationTask(username, email, password);
            userRegistrationTask.execute((Void) null);

        }
    });
}


public class UserRegistrationTask extends AsyncTask<Void, Void, Boolean> {

    private final String mUsername;
    private final String mEmail;
    private final String mPassword;

    UserRegistrationTask(String username, String email, String password) {
        mUsername = username;
        mEmail = email;
        mPassword = password;
    }

    @Override
    protected Boolean doInBackground(Void... params) {
        // TODO: attempt authentication against a network service.

        try {
            URL url = new URL("http://dancecrm.ru/templates/register.php");
            Map<String,Object> requestParams = new LinkedHashMap<>();
            requestParams.put("name", mUsername);
            requestParams.put("email", mEmail);
            requestParams.put("password", mPassword);

            StringBuilder postData = new StringBuilder();
            for (Map.Entry<String,Object> param : requestParams.entrySet()) {
                if (postData.length() != 0) postData.append('&');
                postData.append(URLEncoder.encode(param.getKey(), "UTF-8"));
                postData.append('=');
                postData.append(URLEncoder.encode(String.valueOf(param.getValue()), "UTF-8"));
            }
            byte[] postDataBytes = postData.toString().getBytes("UTF-8");

            HttpURLConnection conn = (HttpURLConnection)url.openConnection();
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            conn.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));
            conn.setDoOutput(true);
            conn.getOutputStream().write(postDataBytes);
            conn.getResponseCode();
        } catch (Exception e) {
            e.printStackTrace();
        }


        // TODO: register the new account here.
        return true;
    }

 }
}

<?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="devs.mulham.raee.sample">

      <uses-permission android:name="android.permission.INTERNET" />

      <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:theme="@style/AppTheme">
        <activity
          android:name=".RegistrationActivity"
          android:theme="@style/AppTheme.NoActionBar">
          <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
          </intent-filter>
        </activity>
        <activity android:name=".MainActivity"/>
      </application>

    </manifest>