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针对事件提供统一订阅，发布以达到组件间通信的解决方案。
Otto is an event bus designed to decouple different parts of your application while still allowing them to communicate efficiently.
观察者模式 + 注解 + 反射
这里要注意几点点：
（1）Otto使用注解定义订阅/发布者的角色，@Subscribe为订阅者，@Produce为发布者，方法名称就可以自定义了。
（2）Otto为了性能，代码意图清晰，@Subscribe，@Produce方法必须定义在直接的作用类上，而不能定义在基类而被继承。
（3）订阅者/发布者均需要register和unregister，而EventBus的发布者是不需要的。
（4）事件参数数量只可以有一个，不可更多
定义事件-LocationChangedEvent ，作为组件间通信传递数据的载体
/*
* 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;
public class LocationChangedEvent {
public final float lat;
public final float lon;
public LocationChangedEvent(float lat, float lon) {
this.lat = lat;
this.lon = lon;
}
@Override public String toString() {
return new StringBuilder("(") //
.append(lat) //
.append(", ") //
.append(lon) //
.append(")") //
.toString();
}
}
避免浪费，相对于BusProvider.getInstance(), Otto需要自己实现单例。
/*
* 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.
}
}
定义订阅者，在接受事件的方法加上修饰符@Subscribe
/*
* 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 android.os.Bundle;
import android.support.v4.app.ListFragment;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Toast;
import com.squareup.otto.Subscribe;
import java.util.ArrayList;
import java.util.List;
/** Maintain a scrollable history of location events. */
public class LocationHistoryFragment extends ListFragment {
private final List<String> locationEvents = new ArrayList<String>();
private ArrayAdapter<String> adapter;
@Override
public void onResume() {
super.onResume();
BusProvider.getInstance().register(this);
}
@Override
public void onPause() {
super.onPause();
BusProvider.getInstance().unregister(this);
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
adapter = new ArrayAdapter<String>(getActivity(),
android.R.layout.simple_list_item_1, locationEvents);
setListAdapter(adapter);
}
@Subscribe
public void onLocationChanged(LocationChangedEvent event) {
locationEvents.add(0, event.toString());
if (adapter != null) {
adapter.notifyDataSetChanged();
}
}
/**
* 方法随便取，参数只能唯一
* 很方便
* @param event
*/
@Subscribe
public void turboLocationChanged(LocationChangedEvent event) {
Toast.makeText(getActivity(), event.toString(), Toast.LENGTH_LONG)
.show();
}
@Subscribe
public void onLocationCleared(LocationClearEvent event) {
locationEvents.clear();
if (adapter != null) {
adapter.notifyDataSetChanged();
}
}
}
定义发布者，通过post()方法在任何地方发布消息了
/*
* 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 android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.View;
import com.squareup.otto.Produce;
import java.util.Random;
import static android.view.View.OnClickListener;
public class LocationActivity extends FragmentActivity {
public static final float DEFAULT_LAT = 40.440866f;
public static final float DEFAULT_LON = -79.994085f;
private static final float OFFSET = 0.1f;
private static final Random RANDOM = new Random();
private static float lastLatitude = DEFAULT_LAT;
private static float lastLongitude = DEFAULT_LON;
@Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.location_history);
findViewById(R.id.clear_location).setOnClickListener(new OnClickListener() {
@Override public void onClick(View v) {
// Tell everyone to clear their location history.
BusProvider.getInstance().post(new LocationClearEvent());
// Post new location event for the default location.
lastLatitude = DEFAULT_LAT;
lastLongitude = DEFAULT_LON;
BusProvider.getInstance().post(produceLocationEvent());
}
});
findViewById(R.id.move_location).setOnClickListener(new OnClickListener() {
@Override public void onClick(View v) {
lastLatitude += (RANDOM.nextFloat() * OFFSET * 2) - OFFSET;
lastLongitude += (RANDOM.nextFloat() * OFFSET * 2) - OFFSET;
BusProvider.getInstance().post(produceLocationEvent());
}
});
}
@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);
}
@Produce public LocationChangedEvent produceLocationEvent() {
// Provide an initial value for location based on the last known position.
return new LocationChangedEvent(lastLatitude, lastLongitude);
}
}
DOWNLOAD ADDRESS（DEMO下载地址）：
http://download.csdn.net/download/yuanyang5917/8660175
事件总线OTTO（助Android深层次解耦——跟回调说拜拜）
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原文地址：http://blog.csdn.net/yuanyang5917/article/details/45482457
