EditHistory.java

/***
 Copyright (c) 2016 CommonsWare, LLC
 Licensed under the Apache License, Version 2.0 (the "License"); you may not
 use this file except in compliance with the License. You may obtain a copy
 of the License at http://www.apache.org/licenses/LICENSE-2.0. Unless required
 by applicable law or agreed to in writing, software distributed under the
 License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
 OF ANY KIND, either express or implied. See the License for the specific
 language governing permissions and limitations under the License.

 Covered in detail in the book _The Busy Coder's Guide to Android Development_
 https://commonsware.com/Android
 */

package com.commonsware.android.tte;

import android.content.Context;
import android.content.SharedPreferences;
import android.net.Uri;
import android.preference.PreferenceManager;
import android.util.JsonReader;
import android.util.JsonWriter;
import android.util.Log;
import org.greenrobot.eventbus.EventBus;
import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicReference;

public class EditHistory {
  public static final EditHistory INSTANCE=new EditHistory();
  private static final String PREF_OPEN_EDITORS="open";
  private AtomicReference<SharedPreferences> prefsRef=
    new AtomicReference<SharedPreferences>();

  public boolean initialize(Context ctxt) {
    if (prefsRef.get()==null) {
      new LoadThread(ctxt).start();

      return(false);
    }

    return(true);
  }

  public List<Uri> getOpenEditors() {
    String editors=prefsRef.get().getString(PREF_OPEN_EDITORS, null);
    ArrayList<Uri> result=new ArrayList<Uri>();

    if (editors!=null) {
      StringReader sr=new StringReader(editors);
      JsonReader json=new JsonReader(sr);

      try {
        json.beginArray();

        while (json.hasNext()) {
          result.add(Uri.parse(json.nextString()));
        }

        json.endArray();
        json.close();
      }
      catch (IOException e) {
        Log.e(getClass().getSimpleName(),
          "Exception reading JSON", e);
      }
    }

    return(result);
  }

  public boolean addOpenEditor(Uri document) {
    List<Uri> current=getOpenEditors();

    if (!current.contains(document)) {
      if (current.size()>9) {
        current.remove(0);
      }

      current.add(document);

      return(saveHistory(current));
    }

    return(true);
  }

  public boolean removeOpenEditor(Uri document) {
    List<Uri> current=getOpenEditors();

    current.remove(document);

    return(saveHistory(current));
  }

  private boolean saveHistory(List<Uri> history) {
    StringWriter sw=new StringWriter();
    JsonWriter json=new JsonWriter(sw);

    try {
      json.beginArray();

      for (Uri uri : history) {
        json.value(uri.toString());
      }

      json.endArray();
      json.close();

      prefsRef
        .get()
        .edit()
        .putString(PREF_OPEN_EDITORS, sw.toString())
        .apply();
    }
    catch (IOException e) {
      Log.e(getClass().getSimpleName(),
        "Exception saving JSON", e);

      return(false);
    }

    return(true);
  }

  public static class InitializedEvent {

  }

  private class LoadThread extends Thread {
    private final Context ctxt;

    LoadThread(Context ctxt) {
      this.ctxt=ctxt.getApplicationContext();
    }

    @Override
    public void run() {
      prefsRef.set(PreferenceManager.getDefaultSharedPreferences(ctxt));
      EventBus.getDefault().post(new InitializedEvent());
    }
  }
}