shell/platform/android/io/flutter/embedding/engine/systemchannels/KeyboardChannel.java

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package io.flutter.embedding.engine.systemchannels;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import io.flutter.plugin.common.BinaryMessenger;
import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.StandardMethodCodec;
import java.util.HashMap;
import java.util.Map;

/**
 * Event message channel for keyboard events to/from the Flutter framework.
 *
 * <p>Receives asynchronous messages from the framework to query the engine known pressed state.
 */
public class KeyboardChannel {
  public final MethodChannel channel;
  private KeyboardMethodHandler keyboardMethodHandler;

  @NonNull
  public final MethodChannel.MethodCallHandler parsingMethodHandler =
      new MethodChannel.MethodCallHandler() {
        Map<Long, Long> pressedState = new HashMap<>();

        @Override
        public void onMethodCall(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
          if (keyboardMethodHandler == null) {
            // Returns an empty pressed state when the engine did not get a chance to register
            // a method handler for this channel.
            result.success(pressedState);
          } else {
            switch (call.method) {
              case "getKeyboardState":
                try {
                  pressedState = keyboardMethodHandler.getKeyboardState();
                } catch (IllegalStateException exception) {
                  result.error("error", exception.getMessage(), null);
                }
                result.success(pressedState);
                break;
              default:
                result.notImplemented();
                break;
            }
          }
        }
      };

  public KeyboardChannel(@NonNull BinaryMessenger messenger) {
    channel = new MethodChannel(messenger, "flutter/keyboard", StandardMethodCodec.INSTANCE);
    channel.setMethodCallHandler(parsingMethodHandler);
  }

  /**
   * Sets the {@link KeyboardMethodHandler} which receives all requests to query the keyboard state.
   */
  public void setKeyboardMethodHandler(@Nullable KeyboardMethodHandler keyboardMethodHandler) {
    this.keyboardMethodHandler = keyboardMethodHandler;
  }

  public interface KeyboardMethodHandler {
    /**
     * Returns the keyboard pressed states.
     *
     * @return A map whose keys are physical keyboard key IDs and values are the corresponding
     *     logical keyboard key IDs.
     */
    Map<Long, Long> getKeyboardState();
  }
}