startService和bindService

startService和bindService同时调用后, 必须对应调用stop和unbind，Service才会destroy。

一个已经存活的Service被bind过，然后解绑后重新bind，Service的onBind方法可能不会再次被调用，因为intent相同：

public boolean filterEquals(Intent other) {        if (other == null) {            return false;        }        // 比较Intent中的各项指标：Action，Uri，MIME type，包名，Component，Category        if (!Objects.equals(this.mAction, other.mAction)) return false;        if (!Objects.equals(this.mData, other.mData)) return false;        if (!Objects.equals(this.mType, other.mType)) return false;        if (!Objects.equals(this.mPackage, other.mPackage)) return false;        if (!Objects.equals(this.mComponent, other.mComponent)) return false;        if (!Objects.equals(this.mCategories, other.mCategories)) return false;        return true;    }

官方文档中说，如果多个client绑定服务，那么服务只有在第一次会执行onBind，如下：

如果你的Service被start, 并且被bind,那么当解除所有绑定, 系统调用onUnbind的, 你可以在onUnbind中返回true, 这样你你可以在下次bindService的时候, 可以回调onRebind(不会回调onBind了, 放心吧), onRebind方法返回值void, 但是client仍然可以拿到IBinder对象(这是因为IBind对象被系统缓存起来了)，onUnbind中返回false,那么依然会回调onBind.

public interface ServiceConnection {    /**     * Called when a connection to the Service has been established, with     * the {@link android.os.IBinder} of the communication channel to the     * Service.     *     * @param name The concrete component name of the service that has     * been connected.     *     * @param service The IBinder of the Service's communication channel,     * which you can now make calls on.     */    public void onServiceConnected(ComponentName name, IBinder service);    /**     * Called when a connection to the Service has been lost.  This typically     * happens when the process hosting the service has crashed or been killed.     * This does <em>not</em> remove the ServiceConnection itself -- this     * binding to the service will remain active, and you will receive a call     * to {@link #onServiceConnected} when the Service is next running.     *     * @param name The concrete component name of the service whose     * connection has been lost.     */    public void onServiceDisconnected(ComponentName name);}

onServiceDisconnected只有在Service链接异常丢失的时候才会调用，主动unbindService,不会调用onServiceDisconnected。

onServiceConnected和onServiceDisconnected都是在UI线程调用.