Add DutyCycleEncoder channel constructor (#2158)

Avoids extra boilerplate at user level.

wpilibc/src/main/native/cpp/DutyCycleEncoder.cpp

@@ -8,6 +8,7 @@
 #include "frc/DutyCycleEncoder.h"
 
 #include "frc/Counter.h"
+#include "frc/DigitalInput.h"
 #include "frc/DigitalSource.h"
 #include "frc/DriverStation.h"
 #include "frc/DutyCycle.h"
@@ -15,6 +16,12 @@
 
 using namespace frc;
 
+DutyCycleEncoder::DutyCycleEncoder(int channel)
+    : m_dutyCycle{std::make_shared<DutyCycle>(
+          std::make_shared<DigitalInput>(channel))},
+      m_analogTrigger{m_dutyCycle.get()},
+      m_counter{} {}
+
 DutyCycleEncoder::DutyCycleEncoder(DutyCycle& dutyCycle)
     : m_dutyCycle{&dutyCycle, NullDeleter<DutyCycle>{}},
       m_analogTrigger{m_dutyCycle.get()},

wpilibc/src/main/native/include/frc/DutyCycleEncoder.h

@@ -32,6 +32,13 @@ class DutyCycleEncoder : public ErrorBase,
                          public Sendable,
                          public SendableHelper<DutyCycleEncoder> {
  public:
+  /**
+   * Construct a new DutyCycleEncoder on a specific channel.
+   *
+   * @param channel the channel to attach to
+   */
+  explicit DutyCycleEncoder(int channel);
+
   /**
    * Construct a new DutyCycleEncoder attached to an existing DutyCycle object.
    *

wpilibcExamples/src/main/cpp/examples/DutyCycleEncoder/cpp/Robot.cpp

@@ -5,17 +5,13 @@
 /* the project.                                                               */
 /*----------------------------------------------------------------------------*/
 
-#include <frc/DigitalInput.h>
-#include <frc/DutyCycle.h>
 #include <frc/DutyCycleEncoder.h>
 #include <frc/TimedRobot.h>
 #include <frc/smartdashboard/SmartDashboard.h>
 
 class Robot : public frc::TimedRobot {
-  frc::DigitalInput m_input{0};  // Input channel
-
-  // Duty cycle encoder
-  frc::DutyCycleEncoder m_dutyCycleEncoder{m_input};
+  // Duty cycle encoder on channel 0
+  frc::DutyCycleEncoder m_dutyCycleEncoder{0};
 
  public:
   void RobotInit() override {

wpilibj/src/main/java/edu/wpi/first/wpilibj/DutyCycleEncoder.java

@@ -33,6 +33,16 @@ public class DutyCycleEncoder implements Sendable, AutoCloseable {
   protected SimDouble m_simPosition;
   protected SimBoolean m_simIsConnected;
 
+  /**
+   * Construct a new DutyCycleEncoder on a specific channel.
+   *
+   * @param channel the channel to attach to
+   */
+  public DutyCycleEncoder(int channel) {
+    m_dutyCycle = new DutyCycle(new DigitalInput(channel));
+    init();
+  }
+
   /**
    * Construct a new DutyCycleEncoder attached to an existing DutyCycle object.
    *

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/dutycycleencoder/Robot.java

@@ -7,20 +7,17 @@
 
 package edu.wpi.first.wpilibj.examples.dutycycleencoder;
 
-import edu.wpi.first.wpilibj.DigitalInput;
 import edu.wpi.first.wpilibj.DutyCycleEncoder;
 import edu.wpi.first.wpilibj.TimedRobot;
 import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;
 
 @SuppressWarnings({"PMD.SingularField"})
 public class Robot extends TimedRobot {
-  private DigitalInput m_input;
   private DutyCycleEncoder m_dutyCycleEncoder;
 
   @Override
   public void robotInit() {
-    m_input = new DigitalInput(0);
-    m_dutyCycleEncoder = new DutyCycleEncoder(m_input);
+    m_dutyCycleEncoder = new DutyCycleEncoder(0);
 
     // Set to 0.5 units per rotation
     m_dutyCycleEncoder.setDistancePerRotation(0.5);