增加 Netty 框架的心跳机制，防止网络波动情况下异常的问题

增加 Netty 框架的心跳机制，防止网络波动情况下异常的问题

pipeline.addLast(new IdleStateHandler(0,
        0,2, TimeUnit.MINUTES));

处理：

@Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
    super.userEventTriggered(ctx, evt);
    if (evt instanceof IdleStateEvent) {
        IdleStateEvent event = (IdleStateEvent) evt;
        if (event.state().equals(IdleState.READER_IDLE)) {
            Logger.i(TAG, "userEventTriggered READER_IDLE 读超时，长期没收到服务器推送数据！Channel is active：" + mChannelFuture.channel().isActive());
            //可以选择重新连接
        } else if (event.state().equals(IdleState.WRITER_IDLE)) {
            Logger.i(TAG, "userEventTriggered WRITER_IDLE 写超时，长期未向服务器发送数据！Channel is active：" + mChannelFuture.channel().isActive());
            //发送心跳包
            ctx.writeAndFlush(HEART_BEAT_STRING);
        } else if (event.state().equals(IdleState.ALL_IDLE)) {
            Logger.i(TAG, "userEventTriggered ALL 没有接收或发送数据一段时间");
            //发送心跳包
            ctx.writeAndFlush(HEART_BEAT_STRING);
        }
    }
}