android开源项目之OTTO事件总线（二）官方demo解说

官方demo见  https://github.com/square/otto

注意自己该编译版本为2.3以上，默认的1.6不支持match_parent属性，导致布局文件出错。

另外需要手动添加android-support-v4和otto到自己的libs文件夹。

主要代码逻辑：

1，在主页面点clear按钮，发布两个事件并传递对象。

2，然后LocationHistoryFragment接收事件对象，并处理。

1，BusProvider提供一个全局唯一的Bus实例对象

调用的时候使用MyProvider.getBusInstance()

/*
 * Copyright (C) 2012 Square, Inc.
 *
 * 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.
 */

package com.squareup.otto.sample;

import com.squareup.otto.Bus;

/**
 * Maintains a singleton instance for obtaining the bus. Ideally this would be replaced with a more efficient means
 * such as through injection directly into interested classes.
 */
public final class BusProvider {
  private static final Bus BUS = new Bus();

  public static Bus getInstance() {
    return BUS;
  }

  private BusProvider() {
    // No instances.
  }
}

2，LocationActivity为主页面

点击clear按钮会发布两个事件对象，LocationClearEvent和LocationChangedEvent

  findViewById(R.id.clear_location).setOnClickListener(new OnClickListener() {
      @Override public void onClick(View v) {
        // Tell everyone to clear their location history.
          //清除位置
        BusProvider.getInstance().post(new LocationClearEvent());

        // Post new location event for the default location.
        //重新加载默认的位置
        lastLatitude = DEFAULT_LAT;
        lastLongitude = DEFAULT_LON;
        BusProvider.getInstance().post(produceLocationEvent());
      }
    });

要使用事件总线别忘了注册和反注册

  @Override protected void onResume() {
    super.onResume();

    // Register ourselves so that we can provide the initial value.
    BusProvider.getInstance().register(this);
  }

  @Override protected void onPause() {
    super.onPause();

    // Always unregister when an object no longer should be on the bus.
    BusProvider.getInstance().unregister(this);
  }

3，上文提到的事件发送时要传递的两个对象LocationChangedEvent对象和LocationClearEvent

可以根据自己喜好，任意设置对象。代码见demo

4，LocationHistoryFragment里接收事件对象

同样需要注册和反注册。有时我们在服务里发布事件，则无需注册

  @Subscribe public void onLocationChanged(LocationChangedEvent event) {
    locationEvents.add(0, event.toString());
    if (adapter != null) {
      adapter.notifyDataSetChanged();
    }
  }

  @Subscribe public void onLocationCleared(LocationClearEvent event) {
    locationEvents.clear();
    if (adapter != null) {
      adapter.notifyDataSetChanged();
    }