ProcessTextChannel.java

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// 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 android.content.pm.PackageManager;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import io.flutter.embedding.engine.dart.DartExecutor;
import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.StandardMethodCodec;
import java.util.ArrayList;
import java.util.Map;
 
/**
 * {@link ProcessTextChannel} is a platform channel that is used by the framework to initiate text
 * processing feature in the embedding and for the embedding to send back the results.
 *
 * <p>When the framework needs to query the list of text processing actions (for instance to expose
 * them in the selected text context menu), it will send to the embedding the message {@code
 * ProcessText.queryTextActions}. In response, the {@link io.flutter.plugin.text.ProcessTextPlugin}
 * will return a map of all activities that can process text. The map keys are generated IDs and the
 * values are the activities labels. On the first request, the {@link
 * io.flutter.plugin.text.ProcessTextPlugin} will make a call to Android's package manager to query
 * all activities that can be performed for the {@code Intent.ACTION_PROCESS_TEXT} intent.
 *
 * <p>When a text processing action has to be executed, the framework will send to the embedding the
 * message {@code ProcessText.processTextAction} with the {@code int id} of the choosen text action
 * and the {@code String} of text to process as arguments. In response, the {@link
 * io.flutter.plugin.text.ProcessTextPlugin} will make a call to the Android application activity to
 * start the activity exposing the text action. The {@link io.flutter.plugin.text.ProcessTextPlugin}
 * will return the processed text if there is one, or null if the activity did not return a
 * transformed text.
 *
 * <p>{@link io.flutter.plugin.text.ProcessTextPlugin} implements {@link ProcessTextMethodHandler}
 * that parses incoming messages from Flutter.
 */
public class ProcessTextChannel {
  private static final String TAG = "ProcessTextChannel";
  private static final String CHANNEL_NAME = "flutter/processtext";
  private static final String METHOD_QUERY_TEXT_ACTIONS = "ProcessText.queryTextActions";
  private static final String METHOD_PROCESS_TEXT_ACTION = "ProcessText.processTextAction";
 
  public final MethodChannel channel;
  public final PackageManager packageManager;
  private ProcessTextMethodHandler processTextMethodHandler;
 
  @NonNull
  public final MethodChannel.MethodCallHandler parsingMethodHandler =
      new MethodChannel.MethodCallHandler() {
        @Override
        public void onMethodCall(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
          if (processTextMethodHandler == null) {
            return;
          }
          String method = call.method;
          Object args = call.arguments;
          switch (method) {
            case METHOD_QUERY_TEXT_ACTIONS:
              try {
                Map<String, String> actions = processTextMethodHandler.queryTextActions();
                result.success(actions);
              } catch (IllegalStateException exception) {
                result.error("error", exception.getMessage(), null);
              }
              break;
            case METHOD_PROCESS_TEXT_ACTION:
              try {
                final ArrayList<Object> argumentList = (ArrayList<Object>) args;
                String id = (String) (argumentList.get(0));
                String text = (String) (argumentList.get(1));
                boolean readOnly = (boolean) (argumentList.get(2));
                processTextMethodHandler.processTextAction(id, text, readOnly, result);
              } catch (IllegalStateException exception) {
                result.error("error", exception.getMessage(), null);
              }
              break;
            default:
              result.notImplemented();
              break;
          }
        }
      };
 
  public ProcessTextChannel(
      @NonNull DartExecutor dartExecutor, @NonNull PackageManager packageManager) {
    this.packageManager = packageManager;
    channel = new MethodChannel(dartExecutor, CHANNEL_NAME, StandardMethodCodec.INSTANCE);
    channel.setMethodCallHandler(parsingMethodHandler);
  }
 
  /**
   * Sets the {@link ProcessTextMethodHandler} which receives all requests to the text processing
   * feature sent through this channel.
   */
  public void setMethodHandler(@Nullable ProcessTextMethodHandler processTextMethodHandler) {
    this.processTextMethodHandler = processTextMethodHandler;
  }
 
  public interface ProcessTextMethodHandler {
    /** Requests the map of text actions. Each text action has a unique id and a localized label. */
    Map<String, String> queryTextActions();
 
    /**
     * Requests to run a text action on a given input text.
     *
     * @param id The ID of the text action returned by {@code ProcessText.queryTextActions}.
     * @param input The text to be processed.
     * @param readOnly Indicates to the activity if the processed text will be used as read-only.
     *     see
     *     https://developer.android.com/reference/android/content/Intent#EXTRA_PROCESS_TEXT_READONLY
     * @param result The method channel result instance used to reply.
     */
    void processTextAction(
        @NonNull String id,
        @NonNull String input,
        @NonNull boolean readOnly,
        @NonNull MethodChannel.Result result);
  }
}